10
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
If $70 + m + n - 20 = 80$ and $m = 2n$, then what is the value of $n$?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
10
If $70 + m + n - 20 = 80$ and $m = 2n$, then what is the value of $n$?
train