7 days ago, Xylia had a total of 120 brown and yellow stickers. 25% of her stickers were yellow stickers. Today, her older brother gave her some more stickers. As a result, her brown stickers increased by 30%. Now, 50% of her stickers are yellow stickers. How many yellow stickers did her older brother give her?

	Yellow stickers	Brown stickers	Total  stickers
Before	1 u	3 u	120
Change	+ 2.9 u	+ 0.9 u
After	3.9 u	3.9 u
Comparing the brown stickers and yellow stickers in the end	1	1

25% = ²⁵₁₀₀ = ¹₄

Yellow stickers : Brown stickers = 1 : 3

Increase in the number of brown stickers
= 30% x 3 u
= ³⁰₁₀₀ x 3 u
= 0.9 u

50% = ⁵⁰₁₀₀ = ¹₂

In the end
Yellow stickers : Brown stickers = 1 : 1

Number of stickers at first
= 3 u + 1 u
= 4 u 

4 u = 120

1 u = 120 ÷ 4 = 30

Number of yellow stickers that Xylia received from her older brother
= 3.9 u - 1 u
= 2.9 u
= 2.9 x 30
= 87

Answer(s): 87