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?
He has to work off $100-$40=$
<gadget id="calculator">100-40</gadget>
<output>60</output>
60.
So he has to work $60/15=
<gadget id="calculator">60/15</gadget>
<output>4</output>
4 hours.

<result>4</result>