Adam has 80 blue stickers and 260 green stickers.
After buying the same number of stickers,
the ratio of the blue stickers and the green stickers becomes 2 : 5.
How many stickers does he buy?

	Blue	Green	Difference
Before	80	260	180
Change	+ ?	+ ?
After	2 u	5 u	3 u

At first
Difference in the number of stickers
= 260 - 80
= 180

In the end
Number of blue stickers = 2 u
Number of green stickers = 5 u

Difference in the number of stickers in units
= 5 u - 2 u
= 3 u

The difference in the number of stickers between the blue stickers and the green stickers remains unchanged.

3 u = 180

1 u = 180 ÷ 3 = 60

Number of blue stickers that Adam buys
= 2 u - 80
= 2 x 60 - 80
= 120 - 80
= 40

Total number of stickers that Adam buys
= 2 x 40
= 80

Answer(s): 80