If the first term of an arithmetic sequence equals the third minus the second, and the fourth term is $8$, what is the first term?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
If the first term of an arithmetic sequence equals the third minus the second, and the fourth term is $8$, what is the first term?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
2
If the first term of an arithmetic sequence equals the third minus the second, and the fourth term is $8$, what is the first term?
train