-40
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Given that $x+y = 10$ and $2x+y = 13$, evaluate $x^2-y^2$.
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
-40
Given that $x+y = 10$ and $2x+y = 13$, evaluate $x^2-y^2$.
train