Looking for fuller explanation of Hooktheory I 5.3

Looking at the review on the bottom of https://www.hooktheory.com/book1/app#/read/5/3, I cannot determine the steps to get from the question to the answer. I know the reason that I am getting it wrong is that I don’t remember the "usually"s. IOW, this usually is followed by that. I am certain that is necessary to complete the answer.

Could somebody please step me through one at a time to resolving the review question?