So Lidia will spend 4 * 15 = $<<4*15=60>>60 on apps.

She already has $66, so she will be left with 66 - 60 = $<<66-60=6>>6.

# Answer

6
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Lidia bought a new tablet, and she needs to buy some apps for it. One app costs $4 on average, and Lidia needs 15 of them. She has $66 for this purpose. How much money will she be left with if she buys all the apps she needs?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
6
Lidia bought a new tablet, and she needs to buy some apps for it. One app costs $4 on average, and Lidia needs 15 of them. She has $66 for this purpose. How much money will she be left with if she buys all the apps she needs?
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