Mr Brandon bought some pizzas for a group of pupils. There was an equal number of girls and boys. The girls received 3 times as many pizzas as the boys. Each boy ate ¹₅ of a pizza and the boys finished all the pizzas given to them. Each girl ate ¹₁₀ of a pizza and the girls had 12¹₂ pizzas left. How many pizzas did Mr Brandon buy?

	Girls (1)	Boys (2)
Before	3 u	1 u
Change	- 1 p	- 2 p
After	125	0

¹₅ = ²₁₀

Cutting the slices of pizzas into same size. Each pizza was cut into 10 slices. Every girl ate 1 slice of pizza and every boy ate 2 slices of pizza.

Number of slices that the girls had left
= 12¹₂ ÷ ¹₁₀ 
= ²⁵₂ x 10
= 125

3 u - 1 p = 125 --- (1)

1 u - 2 p = 0
1 u = 2 p --- (2)

Make u the same.

(2)_x3
3 u = 6 p --- (3)

Substitute (3) into (1).
3 u - 1 p = 125
6 p - 1 p = 125
5 p = 125

1 p = 125 ÷ 5 = 25

Total number of slices of pizzas for girls
= 125 + 1 p
= 125 + 25
= 150

Total number of slices of pizzas for boys
= 150 ÷ 3
= 50

Total number of slices of pizzas for pupils
= 150 + 50
= 200

Total number of pizzas that Mr Brandon bought
= 200 ÷ 10
= 20

Answer(s): 20