Mark spent 220 dollars to fix his car.  It needed two parts that cost 20 dollars each, and labor cost .5 dollars a minute. How many hours did the mechanic work?
Labor cost is .5*60=
<gadget id="calculator">.5*60</gadget>
<output>30</output>
30 dollars per hour.
The cost for parts is 20*2=$
<gadget id="calculator">20*2</gadget>
<output>40</output>
40.
The total cost for labor is 220-40=$
<gadget id="calculator">220-40</gadget>
<output>180</output>
180.
He spent 180/30=
<gadget id="calculator">180/30</gadget>
<output>6</output>
6 hours on labor.

<result>6</result>