solution: Let Amy's, Ben's, and Chris's ages be $a$, $b$, and $c$, respectively. We have the equations \begin{align*} \tag{1}
  \frac{a+b+c}{3}=6 \Rightarrow a+b+c&=18 \\ \tag{2}
  c-4&=a\\ \tag{3}
  b+4&=\frac{3}{5}(a+4)
  \end{align*} From Equation (3), we have $b=\frac{3}{5}(a+4)-4$. We substitute Equation (2) into Equation (3) to eliminate $a$, to get $b=\frac{3}{5}(c)-4$. Substituting this last equation and Equation (2) into Equation (1) to eliminate $a$ and $b$, we have  \[[c-4]+[\frac{3}{5}(c)-4]+c=18\] Solving for $c$, we find that $c=10$. Thus, Chris's age is $\boxed{10}$.
prompt.content: <|im_start|>system
  You are a helpful assistant.<|im_end|>
  <|im_start|>user
  The average of Amy's, Ben's, and Chris's ages is 6. Four years ago,  Chris was the same age as Amy is now. In four years, Ben's age will be $\frac{3}{5}$ of Amy's age at that time. How many years old is Chris now?
  Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
  <|im_start|>assistant
  
prompt.role: user
extra_info.answer: 10
extra_info.question: The average of Amy's, Ben's, and Chris's ages is 6. Four years ago,  Chris was the same age as Amy is now. In four years, Ben's age will be $\frac{3}{5}$ of Amy's age at that time. How many years old is Chris now?
extra_info.split: test