Jake agrees to work part of his debt off. He owed someone $100 but paid them $40 before agreeing to work off the rest.  He worked for $15 an hour. How many hours did he have to work? Let's answer step by step:
He has to work off $100 - $40 = $60. So he has to work $60 / 15 = 4 hours. The answer: 4.