Answer:
5 hours or less
Step-by-step explanation:
Little hard to see your screen but I think I understand.
Since he has $21 and a coupon for $9 off, he can spend up to $30.
The rental costs $6 per hour so he could rent the boat for up to 5 hours. It would cost him $30 but he get $9 off with the coupon.
So your answer would be 5 hours or less
