If you did not get 6 out of 6 on problem 3 from the exam please redo it and turn in a properly written proof.
Here is the problem:
Let , and be sets. Prove that
Note that you must reason about arbitrary sets — you cannot prove this “by example”. Likewise if you use a truth table then you need to explain why it is relevant and make sure it is a truth table for statements. It makes no sense to say that is true or false if is a set.