When used in training, Solver problems should give answer-based feedback

[vanlehn]

The Solve button currently give feedback on bad syntax and on illegal numbers. During training, it should also give feedback when the answer is incorrect. It should say, "Sorry. None of your variables have a value that matches the correct answer's value. Please revise your model. If you have tried already a few times, then its OK to give up and go on." If the answer is correct, it should say, "Right! One of your variables as a value that matches the correct answer's value." This feature should be used in both the TopoMath and Control conditions of the study.

Of course, the feature should not be used during the pre-test and post-test. The preface to the post-test should say, "The Solve button will no longer tell you if your answer is correct or incorrect."