3
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
If the sum of the second and fourth terms of an arithmetic sequence is $6$, what is the third term?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
3
If the sum of the second and fourth terms of an arithmetic sequence is $6$, what is the third term?
train