diff --git a/main/exercice/answer.class.php b/main/exercice/answer.class.php
index 284cc199bb..3bbc8ccab1 100755
--- a/main/exercice/answer.class.php
+++ b/main/exercice/answer.class.php
@@ -71,7 +71,6 @@ class Answer
         $objExercise = new Exercise($this->course_id);
         $exerciseId = isset($_REQUEST['exerciseId']) ? $_REQUEST['exerciseId'] : null;
         $objExercise->read($exerciseId);
-
         if ($objExercise->random_answers == '1') {
             $this->readOrderedBy('rand()', '');// randomize answers
         } else {
diff --git a/main/exercice/exercise.class.php b/main/exercice/exercise.class.php
index d223b2e82a..b3a9bf72dd 100755
--- a/main/exercice/exercise.class.php
+++ b/main/exercice/exercise.class.php
@@ -1,6 +1,8 @@
 <?php
 /* For licensing terms, see /license.txt */
 
+use ChamiloSession as Session;
+
 /**
  * Class Exercise
  *
@@ -162,9 +164,7 @@ class Exercise
             $this->display_category_name = $object->display_category_name;
             $this->pass_percentage = $object->pass_percentage;
             $this->sessionId = $object->session_id;
-
             $this->is_gradebook_locked = api_resource_is_locked_by_gradebook($id, LINK_EXERCISE);
-
             $this->review_answers = (isset($object->review_answers) && $object->review_answers == 1) ? true : false;
             $this->globalCategoryId = isset($object->global_category_id) ? $object->global_category_id : null;
             $this->questionSelectionType = isset($object->question_selection_type) ? $object->question_selection_type : null;
@@ -190,10 +190,10 @@ class Exercise
             }
 
             if ($object->end_time != '0000-00-00 00:00:00') {
-                $this->end_time 	= $object->end_time;
+                $this->end_time = $object->end_time;
             }
             if ($object->start_time != '0000-00-00 00:00:00') {
-                $this->start_time 	= $object->start_time;
+                $this->start_time = $object->start_time;
             }
 
             //control time
@@ -3757,7 +3757,16 @@ class Exercise
                     }
                     break;
                 case CALCULATED_ANSWER:
-                    $answer = $objAnswerTmp->selectAnswer($_SESSION['calculatedAnswerId'][$questionId]);
+                    $calculatedAnswerId = Session::read('calculatedAnswerId');
+                    $answer = '';
+                    if ($calculatedAnswerId) {
+                        $calculatedAnswerInfo = Session::read('calculatedAnswerInfo');
+                        if (isset($calculatedAnswerInfo[$questionId])) {
+                            $answer = $calculatedAnswerInfo[$questionId];
+                        } else {
+                            $answer = $objAnswerTmp->selectAnswer($calculatedAnswerId[$questionId]);
+                        }
+                    }
                     $preArray = explode('@@', $answer);
                     $last = count($preArray) - 1;
                     $answer = '';
@@ -3823,6 +3832,16 @@ class Exercise
                     }
                     $answer = '';
                     $realCorrectTags = $correctTags;
+
+                    if ($from_database && empty($calculatedAnswerId)) {
+                        $queryfill = "SELECT answer FROM ".$TBL_TRACK_ATTEMPT."
+                                          WHERE
+                                            exe_id = '".$exeId."' AND
+                                            question_id= ".intval($questionId)."";
+                        $resfill = Database::query($queryfill);
+                        $answer = Database::result($resfill, 0, 'answer');
+                    }
+
                     for ($i = 0; $i < count($realCorrectTags); $i++) {
                         if ($i == 0) {
                             $answer .= $realText[0];
diff --git a/main/exercice/exercise_result.php b/main/exercice/exercise_result.php
index 0c068613d9..d37aba233b 100755
--- a/main/exercice/exercise_result.php
+++ b/main/exercice/exercise_result.php
@@ -165,7 +165,6 @@ ExerciseLib::exercise_time_control_delete(
     $learnpath_id,
     $learnpath_item_id
 );
-
 ExerciseLib::delete_chat_exercise_session($exe_id);
 
 if ($origin != 'learnpath') {
@@ -180,6 +179,8 @@ if ($origin != 'learnpath') {
     if (api_is_allowed_to_session_edit()) {
         Session::erase('objExercise');
         Session::erase('exe_id');
+        Session::erase('calculatedAnswerId');
+        Session::erase('calculatedAnswerInfo');
     }
 	Display::display_footer();
 } else {
@@ -190,6 +191,8 @@ if ($origin != 'learnpath') {
     if (api_is_allowed_to_session_edit()) {
         Session::erase('objExercise');
         Session::erase('exe_id');
+        Session::erase('calculatedAnswerId');
+        Session::erase('calculatedAnswerInfo');
     }
 
 	// Record the results in the learning path, using the SCORM interface (API)
diff --git a/main/exercice/exercise_show.php b/main/exercice/exercise_show.php
index bd929c4bb4..6db1c27e3e 100755
--- a/main/exercice/exercise_show.php
+++ b/main/exercice/exercise_show.php
@@ -1,6 +1,8 @@
 <?php
 /* For licensing terms, see /license.txt */
 
+use ChamiloSession as Session;
+
 /**
  *  Shows the exercise results
  *
@@ -12,8 +14,6 @@
  *
  */
 
-use ChamiloSession as Session;
-
 require_once '../inc/global.inc.php';
 $debug = false;
 if (empty($origin) ) {
@@ -27,10 +27,10 @@ if ($origin == 'learnpath') {
 }
 
 // Database table definitions
-$TBL_EXERCISE_QUESTION 	= Database::get_course_table(TABLE_QUIZ_TEST_QUESTION);
-$TBL_QUESTIONS         	= Database::get_course_table(TABLE_QUIZ_QUESTION);
-$TBL_TRACK_EXERCISES    = Database::get_main_table(TABLE_STATISTIC_TRACK_E_EXERCISES);
-$TBL_TRACK_ATTEMPT		= Database::get_main_table(TABLE_STATISTIC_TRACK_E_ATTEMPT);
+$TBL_EXERCISE_QUESTION = Database::get_course_table(TABLE_QUIZ_TEST_QUESTION);
+$TBL_QUESTIONS = Database::get_course_table(TABLE_QUIZ_QUESTION);
+$TBL_TRACK_EXERCISES = Database::get_main_table(TABLE_STATISTIC_TRACK_E_EXERCISES);
+$TBL_TRACK_ATTEMPT = Database::get_main_table(TABLE_STATISTIC_TRACK_E_ATTEMPT);
 
 // General parameters passed via POST/GET
 if ($debug) { error_log('Entered exercise_result.php: '.print_r($_POST,1)); }
@@ -77,13 +77,13 @@ if (empty($track_exercise_info)) {
     api_not_allowed(true);
 }
 
-$exercise_id        = $track_exercise_info['id'];
-$exercise_date      = $track_exercise_info['start_date'];
-$student_id         = $track_exercise_info['exe_user_id'];
-$learnpath_id       = $track_exercise_info['orig_lp_id'];
-$learnpath_item_id  = $track_exercise_info['orig_lp_item_id'];
-$lp_item_view_id    = $track_exercise_info['orig_lp_item_view_id'];
-$current_user_id    = api_get_user_id();
+$exercise_id = $track_exercise_info['id'];
+$exercise_date = $track_exercise_info['start_date'];
+$student_id = $track_exercise_info['exe_user_id'];
+$learnpath_id = $track_exercise_info['orig_lp_id'];
+$learnpath_item_id = $track_exercise_info['orig_lp_item_id'];
+$lp_item_view_id = $track_exercise_info['orig_lp_item_view_id'];
+$current_user_id = api_get_user_id();
 
 if (api_is_excluded_user_type(true, $student_id)) {
     api_not_allowed(true);
@@ -116,7 +116,7 @@ $fromlink = '';
 
 $interbreadcrumb[]= array("url" => "exercise.php?".api_get_cidreq(),"name" => get_lang('Exercises'));
 $interbreadcrumb[]= array("url" => "overview.php?exerciseId=".$exercise_id.'&'.api_get_cidreq(),"name" => $objExercise->name);
-$interbreadcrumb[]= array("url" => "#","name" => get_lang('Result'));
+$interbreadcrumb[]= array("url" => "#", "name" => get_lang('Result'));
 
 $this_section = SECTION_COURSES;
 
@@ -300,7 +300,6 @@ foreach ($questionList as $questionId) {
 $counter = 1;
 $exercise_content = null;
 $category_list = array();
-
 $useAdvancedEditor = true;
 
 if (!empty($maxEditors) && count($questionList) > $maxEditors) {
@@ -313,10 +312,10 @@ foreach ($questionList as $questionId) {
 	// destruction of the Question object
 	unset($objQuestionTmp);
 
-	// creates a temporary Question object
-	$objQuestionTmp 	= Question::read($questionId);
-	$questionWeighting	= $objQuestionTmp->selectWeighting();
-	$answerType			= $objQuestionTmp->selectType();
+    // creates a temporary Question object
+    $objQuestionTmp = Question::read($questionId);
+    $questionWeighting = $objQuestionTmp->selectWeighting();
+    $answerType = $objQuestionTmp->selectType();
 
 	// Start buffer
     ob_start();
@@ -383,6 +382,20 @@ foreach ($questionList as $questionId) {
         );
         $questionScore = $question_result['score'];
         $totalScore += $question_result['score'];
+    } elseif ($answerType == CALCULATED_ANSWER) {
+        $question_result = $objExercise->manage_answer(
+            $id,
+            $questionId,
+            $choice,
+            'exercise_show',
+            array(),
+            false,
+            true,
+            $show_results,
+            $objExercise->selectPropagateNeg()
+        );
+        $questionScore = $question_result['score'];
+        $totalScore += $question_result['score'];
     } elseif ($answerType == GLOBAL_MULTIPLE_ANSWER) {
         $question_result = $objExercise->manage_answer(
             $id,
@@ -610,7 +623,8 @@ foreach ($questionList as $questionId) {
             }
 
             //showing the score
-            $queryfree = "select marks from ".$TBL_TRACK_ATTEMPT." WHERE exe_id = ".intval($id)." and question_id= ".intval($questionId)."";
+            $queryfree = "SELECT marks FROM ".$TBL_TRACK_ATTEMPT." 
+                          WHERE exe_id = ".intval($id)." and question_id= ".intval($questionId)."";
             $resfree = Database::query($queryfree);
             $questionScore= Database::result($resfree,0,"marks");
             $totalScore+=$questionScore;
@@ -675,7 +689,13 @@ foreach ($questionList as $questionId) {
 				}
 			}
             echo '<br />';
-            echo Display::url($url_name, 'javascript://', array('class' => 'btn', 'onclick'=>"showfck('".$name."', '".$marksname."');"));
+            echo Display::url(
+                $url_name,
+                'javascript://',
+                array(
+                    'class' => 'btn btn-default',
+                    'onclick' => "showfck('".$name."', '".$marksname."');")
+            );
 			echo '<br />';
 
             echo '<div id="feedback_'.$name.'" style="width:100%">';
@@ -804,9 +824,9 @@ foreach ($questionList as $questionId) {
     $score = array();
     if ($show_results) {
 		$score['result'] = get_lang('Score')." : ".ExerciseLib::show_score($my_total_score, $my_total_weight, false, false);
-        $score['pass']   = $my_total_score >= $my_total_weight ? true : false;
-        $score['type']   = $answerType;
-        $score['score']  = $my_total_score;
+        $score['pass'] = $my_total_score >= $my_total_weight ? true : false;
+        $score['type'] = $answerType;
+        $score['score'] = $my_total_score;
         $score['weight'] = $my_total_weight;
         $score['comments'] = isset($comnt) ? $comnt : null;
     }
@@ -815,11 +835,9 @@ foreach ($questionList as $questionId) {
 	$i++;
 
     $contents = ob_get_clean();
-
     $question_content = '<div class="question_row">';
-
  	if ($show_results) {
-        //Shows question title an description
+        // Shows question title an description
 	    $question_content .= $objQuestionTmp->return_header(null, $counter, $score);
 	}
 	$counter++;
diff --git a/main/inc/ajax/exercise.ajax.php b/main/inc/ajax/exercise.ajax.php
index 3b23af281e..383d99c077 100755
--- a/main/inc/ajax/exercise.ajax.php
+++ b/main/inc/ajax/exercise.ajax.php
@@ -351,8 +351,7 @@ switch ($action) {
                     continue;
                 }
 
-                $my_choice = isset($choice[$my_question_id]) ?
-                    $choice[$my_question_id] : null;
+                $my_choice = isset($choice[$my_question_id]) ? $choice[$my_question_id] : null;
 
                 if ($debug) {
                     error_log("my_choice = ".print_r($my_choice, 1)."");
@@ -362,7 +361,7 @@ switch ($action) {
                 $objQuestionTmp = Question::read($my_question_id, $course_id);
 
                 // Getting free choice data.
-                if ($objQuestionTmp->type  == FREE_ANSWER && $type == 'all') {
+                if ($objQuestionTmp->type == FREE_ANSWER && $type == 'all') {
                     $my_choice = isset($_REQUEST['free_choice'][$my_question_id]) && !empty($_REQUEST['free_choice'][$my_question_id]) ? $_REQUEST['free_choice'][$my_question_id]: null;
                 }
 
diff --git a/main/inc/lib/exercise.lib.php b/main/inc/lib/exercise.lib.php
index 241b35d1ce..58ff05b08e 100644
--- a/main/inc/lib/exercise.lib.php
+++ b/main/inc/lib/exercise.lib.php
@@ -622,17 +622,20 @@ class ExerciseLib
                      * the text to find mustn't contains HTML tags
                      * the text to find mustn't contains char "
                      */
-                    if ($origin !== null) {
-                        global $exe_id;
-                        $trackAttempts = Database::get_main_table(
-                            TABLE_STATISTIC_TRACK_E_ATTEMPT
-                        );
-                        $sql = 'SELECT answer FROM ' . $trackAttempts . '
-                                WHERE exe_id=' . $exe_id . ' AND question_id=' . $questionId;
-                        $rsLastAttempt = Database::query($sql);
-                        $rowLastAttempt = Database::fetch_array($rsLastAttempt);
-                        $answer = $rowLastAttempt['answer'];
-                        if (empty($answer)) {
+                    global $exe_id;
+                    $trackAttempts = Database::get_main_table(
+                        TABLE_STATISTIC_TRACK_E_ATTEMPT
+                    );
+                    $sql = 'SELECT answer FROM ' . $trackAttempts . '
+                            WHERE exe_id=' . $exe_id . ' AND question_id=' . $questionId;
+                    $rsLastAttempt = Database::query($sql);
+                    $rowLastAttempt = Database::fetch_array($rsLastAttempt);
+                    $answer = $rowLastAttempt['answer'];
+
+                    $calculatedAnswerId = Session::read('calculatedAnswerId');
+                    $calculatedAnswerInfo = Session::read('calculatedAnswerInfo');
+                    if (empty($answer)) {
+                        if (empty($calculatedAnswerId)) {
                             $_SESSION['calculatedAnswerId'][$questionId] = mt_rand(
                                 1,
                                 $nbrAnswers
@@ -640,6 +643,14 @@ class ExerciseLib
                             $answer = $objAnswerTmp->selectAnswer(
                                 $_SESSION['calculatedAnswerId'][$questionId]
                             );
+
+                            Session::write('calculatedAnswerInfo', [$questionId => $answer]);
+
+                        } else {
+                            $calculatedAnswerInfo = Session::read('calculatedAnswerInfo');
+                            if (isset($calculatedAnswerInfo[$questionId])) {
+                                $answer = $calculatedAnswerInfo[$questionId];
+                            }
                         }
                     }
 
@@ -651,6 +662,7 @@ class ExerciseLib
                         $correctAnswerList
                     );
 
+
                     // get student answer to display it if student go back to previous calculated answer question in a test
                     if (isset($user_choice[0]['answer'])) {
                         api_preg_match_all(