normal distribution hypothesis testing

For these normal distribution hypothesis testing questions you either have to test significance or find the critical region. How do I know which one to do?

A question will always ask you if you need to find the critical region. If it’s just a hypothesis test where they want you to test if a single result is significant then there’s no need to find the critical region, and it’s a waste of time to do so.

I've attatched a photo of the question and the answer. In the question they do not ask for the critical region explicitly but you still have to do it. In this question how am I to know that I have to calculate the critical region rather than test for significance?