Nelly wants to purchase pizza for herself and 14 friends, which is a total of 1 + 14 = 15 people.
Each pizza feeds 3 people, so Nelly needs to buy 15/3 = 5 pizzas.
Each pizza costs $12, so 5 pizzas will cost 5 * $12 = $60.
Nelly earns $4 per night babysitting, so she needs to earn $60 to afford the pizza.
To earn $60, Nelly needs to babysit for $60 / $4 = 15 nights.
Therefore, Nelly needs to babysit for 15 nights to afford the pizza.
#### 15
The answer is: 15
Below is a math problem. Provide a detailed, step-by-step solution.

### Problem:
If Nelly wants to purchase pizza for herself and her 14 friends, with each pizza costing $12 and feeding 3 people, and she earns $4 per night babysitting the neighbors' kids, how many nights does she need to babysit in order to afford the pizza?

### Answer:
