Or, "I understand the frustration, failing exams sucks whatever the reason. In this case though, 1+1=2".
The delivery matters, even more so when the person is in a difficult position. Also in this case we don't _know_ that they are wrong, we only think it likely based on assumptions. It's probably more likely that OP said "random" out of frustration, and they've since removed it from their post.
