Tony walks 3 miles at 3 miles per hour for 3/3=1 hour.

Tony also runs 10 miles at 5 miles per hour for 10/5=<<10/5=2>>2 hours.

Thus, each day he exercises for 1+2=<<3=3>>3 hours.

Over the course of one week, he exercises for 3*7=<<3*7=21>>21 hours.

# Answer

21
<|im_start|>system
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<|im_start|>user
Tony exercises every morning by walking 3 miles carrying a 25-pound backpack, then he runs another 10 miles without the backpack.  If he walks at a speed of 3 miles per hour and runs at a speed of 5 miles per hour, how many hours each week does he spend exercising?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
21
Tony exercises every morning by walking 3 miles carrying a 25-pound backpack, then he runs another 10 miles without the backpack.  If he walks at a speed of 3 miles per hour and runs at a speed of 5 miles per hour, how many hours each week does he spend exercising?
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