He spent 10 minutes *9 cars = <<10*9=90>>90 minutes washing cars

He spent another 15 minutes * 6 cars = <<15*6=90>>90 minutes changing oil.

He spent 2 cars * 30 minutes = <<2*30=60>>60 minutes changing tires.

He spent 90 minutes + 90 minutes + 60 minutes = <<90+90+60=240>>240 minutes working

He spent 240 minutes / 60 minutes = <<240/60=4>>4 hours working

# Answer

4
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
It takes 10 minutes to wash a car, 15 minutes to change oil, and 30 minutes to change a set of tires.  If mike washes 9 cars, changes the oil on 6 cars, and changes two sets of tires how many hours did he work?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
4
It takes 10 minutes to wash a car, 15 minutes to change oil, and 30 minutes to change a set of tires.  If mike washes 9 cars, changes the oil on 6 cars, and changes two sets of tires how many hours did he work?
train