human
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?
assistant
How much does he have to work off? ** He has to work off $100-$40=$<<100-40=60>>60.
How many hours does he have to work? ** So he has to work $60/15=<<60/15=4>>4 hours
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