There are a few textbook questions that many students are asking about when they visit, so I here I will put some explanation of some of them that come up most frequently.
This doesn't mean you still aren't allowed to visit or ask about anything, including these questions. But if these written explanations are good enough for you then it might save you some time.
Commentary will be put here:
3.42a: when deriving the cdf be careful of cases x<0 and x >= 0
3.46: two correct answers; depends on choice of dydx or dxdy.
4.9: inventory problem; answer quite involved (and note that the policy is actually to stock n-1 parts once you find the smallest n that satisfies the condition specified.)
4.13: there is the classic proof that is easy when you know the "trick" and the same trick applies to 4.8. The more direct proof using integration by parts is what you might have come up with yourself but there is a actually a tricky mathematical issue to navigate.