She needs to buy 15 / 3 = <<15/3=5>>5 pizzas.

The pizzas cost 5 * $12 = $<<5*12=60>>60 total.

It will take her $60 / $4 = <<60/4=15>>15 nights worth of babysitting to afford the pizza.

# Answer

15
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Nelly wants to buy pizza for herself and her 14 friends. Each pizza costs $12 and can feed 3 people. If Nelly earns $4 a night babysitting the neighbors' kids, how many nights will she have to babysit to afford the pizza?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
15
Nelly wants to buy pizza for herself and her 14 friends. Each pizza costs $12 and can feed 3 people. If Nelly earns $4 a night babysitting the neighbors' kids, how many nights will she have to babysit to afford the pizza?
train