Challenge: Find the cost of one Pizza if 3 Pizzas cost $18

Consider the following problem: 3 pizzas cost $18, what is the cost of 1 Pizza?

The objective is to explain or teach a 2nd grade student that the price of 1 Pizza is $6. Obviously divided 18 by 3 is a bad explanation because the following question from the kid is "Why?".

The best explanation will win a special gift.