Unless you actually somehow think this was a genuine misunderstanding of the test directions, then they were clear and the student provided useless answers on purpose.
Getting points is a reward for giving right answers. If the student wants to play language games on his math exam, let em fuck around and find out. But they do have to find out. Literally all I've suggested is making the student demonstrate actual understanding. Thinking even that is somehow going too far is absolutely ludicrous.
who the hell is joe