Sam and Andy had 80 stickers in total. Andy had 40 stickers more than Sam at first. After Sam and Andy played a game with Yen, Sam had ¹₅ as many stickers as Andy. If Sam lost as many stickers as Andy to Yen, find the number of stickers that Sam lost to Yen.

	Sam	Andy	Difference
Before	1 u	1 u + 40	40
Change	- ?	- ?
After	1 p	5 p	4 p

Total number of stickers at first
= 1 u + 1 u + 40 
= 2 u + 40

2 u + 40 = 80
2 u = 80 - 40
2 u = 40

1 u = 40 ÷ 2 = 20

Since Sam lost the same number of stickers as Andy, the difference in the number of stickers between Sam and Andy at first and in the end remains the same.

Difference in the number of stickers in the end
= 5 p - 1 p
= 4 p

4 p = 40

1 p = 40 ÷ 4 = 10

Number of stickers that Sam lost to Yen
= 1 u - 1 p
= 20 - 1 x 10
= 20 - 10
= 10

Answer(s): 10