Labor cost is .5*60=<<.5*60=30>>30 dollars per hour

The cost for parts is 20*2=$<<20*2=40>>40

The total cost for labor is 220-40=$<<220-40=180>>180

He spent 180/30=<<180/30=6>>6 hours on labor.

# Answer

6
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
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?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
6
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?
train