He paid for 20-6=<<20-6=14>>14 candy bars

So he paid 14*1.5=$<<14*1.5=21>>21

# Answer

21
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
John buys 20 candy bars.  His brother Dave pays for 6 of them.  If each candy bar costs $1.50, how much did John pay?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
21
John buys 20 candy bars.  His brother Dave pays for 6 of them.  If each candy bar costs $1.50, how much did John pay?
train