Lizzy: 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?.
Me: Hmmm, let me think. I think this is the detailed solution:
Labor cost is .5 * 60 = 30 dollars per hour. The cost for parts is 20 * 2 = $40. The total cost for labor is 220 - 40 = $180. He spent 180 / 30 = 6 hours on labor. Final answer: 6.