Question 116310
The supposition that the men paid $27 for their rooms is not correct.  The men paid $25 for their rooms and that $25 is in the cash register. Each man got back $1 and the bellboy kept $2, so $25+$3+$2=$30 or we could look at it another
way:
3*$9=$27 (what they thought they were paying) minus the $2 kept by the bellboy=$25 (what they were actually paying)-- the amount in the cash register.

Actually, this problem has a very good moral to it: "As you go through life, you need to keep track of where the money is"

Hope this helps---ptaylor