A notebook costs $1.50 x 3 = $<<1.5*3=4.50>>4.50.

So Lyle will pay $4.50 x 4 = $<<4*4.5=18>>18 for the 4 notebooks.

# Answer

18
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
A notebook costs three times as much as a pen. If a pen costs $1.50, how much will Lyle pay for 4 notebooks?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
18
A notebook costs three times as much as a pen. If a pen costs $1.50, how much will Lyle pay for 4 notebooks?
train