For each of the following four cases what is the missing amount?

Assets = Liabilities + Capital Stock - Retained Earnings

Case A $23,000 $11,000 missing $ 4,500

This is not enough information. I don't know where those numbers belong.

Essentially you just insert whatever numbers they give you and then solve for the missing number.

However, it's
Assets = Liabilities + Capital Stock + Retained Earnings

The only way retained earnings would be a minus is if they had a deficit. And I doubt they would give you that at this level, and also a deficit would be a negative number -- so you'd be inserting a negative number into retained earnings and it would work itself out automatically.