This is item "c" of question 11 from section 1.2 in Daniel J. Velleman's "How to Prove It - A Structured Approach" (great book).
The question asks that I find a simpler formula equivalent to $\neg (P \wedge \neg Q) \vee (\neg P \wedge Q)$, and the answer at the end of the book is $\neg P \vee Q$. I've tried DeMorgan and the associative and commutative laws, to no avail. I'm at my wit's end. All I got was $(\neg P \vee Q) \vee (\neg P \wedge Q)$.
Any clues? Thanks in advance.