1. Let's start by understanding the problem. Three girls initially pay $100 each, totaling $300. 2. The motel room actually costs $250, so the desk clerk gives $50 to the room attendant to return to the girls. 3. The room attendant gives $10 back to each girl ($30 total), and keeps $20. 4. Now, each girl has effectively paid $90 ($100 - $10), totaling $270. 5. The confusion arises because the problem adds the $20 the attendant kept to the $270 the girls paid, giving $290, which is incorrect. 6. The correct way to account for the money is: - $250 went to the motel for the room. - $20 is with the attendant. - $30 was returned to the girls ($10 each). 7. These add up to $250 + $20 + $30 = $300, the initial amount. 8. The error is in adding the $20 to the $270, instead, the $20 is part of the $270 paid, not in addition to it. Final answer: There is no missing $10. The mistake is in adding the room attendant's $20 to the total amount paid by the girls, which already includes that $20.