$P$ and $Q$ represent numbers, and $P \ast Q$ means $\cfrac{P+Q}{2}$. What is the value of $3 \ast (6 \ast 8)$?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
$P$ and $Q$ represent numbers, and $P \ast Q$ means $\cfrac{P+Q}{2}$. What is the value of $3 \ast (6 \ast 8)$?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
5
$P$ and $Q$ represent numbers, and $P \ast Q$ means $\cfrac{P+Q}{2}$. What is the value of $3 \ast (6 \ast 8)$?
train