diff --git a/question/type/calculated/questiontype.php b/question/type/calculated/questiontype.php
index 2e310c3386a..11250055a50 100644
--- a/question/type/calculated/questiontype.php
+++ b/question/type/calculated/questiontype.php
@@ -763,10 +763,11 @@ class question_calculated_qtype extends question_dataset_dependent_questiontype
         $delimiter = ': ';
         $virtualqtype = $this->get_virtual_qtype();
         foreach ($answers as $answer) {
-            $formula = $answer->answer;
-            foreach ($data as $name => $value) {
+          //  $formula = $answer->answer;
+            $formula = parent::substitute_variables($answer->answer,$data);
+          /*  foreach ($data as $name => $value) {
                 $formula = str_replace('{'.$name.'}', $value, $formula);
-            }
+            }*/
             $formattedanswer = qtype_calculated_calculate_answer(
                     $answer->answer, $data, $answer->tolerance,
                     $answer->tolerancetype, $answer->correctanswerlength,
diff --git a/question/type/datasetdependent/abstractqtype.php b/question/type/datasetdependent/abstractqtype.php
index cb2767107ff..0642b41ef6e 100644
--- a/question/type/datasetdependent/abstractqtype.php
+++ b/question/type/datasetdependent/abstractqtype.php
@@ -82,7 +82,11 @@ class question_dataset_dependent_questiontype extends default_questiontype {
 
     function substitute_variables($str, $dataset) {
         foreach ($dataset as $name => $value) {
-            $str = str_replace('{'.$name.'}', $value, $str);
+            if($value < 0 ){
+                $str = str_replace('{'.$name.'}', '('.$value.')', $str);
+            } else {
+                $str = str_replace('{'.$name.'}', $value, $str);
+            }
         }
         return $str;
     }