refactoring: description added

src/arithmeticSubtraction.c

@@ -14,7 +14,7 @@ float* subtraction_float(float a, float b) {
     *result=a - b;
     return result;
 }
-//arithmetic Subtraction specification double
+//arithmetic Subtraction specification double 3 function
 double* subtraction_double(double a, double b) {
     double* result= malloc(sizeof (double));
     *result=a - b;