Let x be the number of years Tom has been teaching

Devin has been teaching for (1/2)x-5 years

70=x+((1/2)x-5)

70=(3/2)x-5

75=(3/2)x

x=<<50=50>>50

Tom has been teaching for 50 years

# Answer

50
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Tom and Devin have been teaching for a total of 70 years. Devin has been teaching for 5 less than half the number of years that Tom has. How many years has Tom been teaching?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
50
Tom and Devin have been teaching for a total of 70 years. Devin has been teaching for 5 less than half the number of years that Tom has. How many years has Tom been teaching?
train