solution: From the defined function, we know that $5\star 1 = 9(5)+2(1)-(5)(1)+5= 45+2-5+5=\boxed{47}$.
prompt.content: <|im_start|>system
  You are a helpful assistant.<|im_end|>
  <|im_start|>user
  If $a\star b = 9a+2b-ab+5$, what is the value of $5\star1$?
  Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
  <|im_start|>assistant
  
prompt.role: user
extra_info.answer: 47
extra_info.question: If $a\star b = 9a+2b-ab+5$, what is the value of $5\star1$?
extra_info.split: test