A -> B is equivalent to ~A \/ B, so (p v q) ^ not q --> p is equivalent to not((p v q) ^ not q) \/ p, or not(p \/ q) \/ q \/ p. I'll leave you to apply De Morgan one more time, if necessary. Actually, one can already see that not(p \/ q) \/ (p \/ q) is a tautology because it is the law of excluded middle.