There are 25% more purple stickers than yellow stickers in a bag. After Mark removed 40% of the purple stickers and increased the number of yellow stickers by 20%, there are now 108 fewer purple stickers than yellow stickers. Find the number of yellow stickers at first.

	Purple	Yellow
Before	5 u	4 u
Change	- 2 u	+ 0.8 u
After	3 u	4.8 u

Number of purple stickers in percentage
= 100% + 25%
= 125%

125% = ¹²⁵₁₀₀ = ⁵₄

Number of purple stickers that Mark removed
= 40% x 5 u
= ⁴⁰₁₀₀ x 5 u 
= 2 u

Number of yellow stickers that Mark increased 
= 20% x 4 u
= ²⁰₁₀₀  x 4 u
= 0.8 u

Number of purple stickers in the end
= 5 u - 2 u
= 3 u

Number of yellow stickers in the end
= 4 u + 0.8 u
= 4.8 u

Number of fewer purple stickers than yellow stickers in the end
= 4.8 u - 3 u 
= 1.8 u 

1.8 u = 108

1 u = 108 ÷ 1.8 = 60

Number of yellow stickers at first
= 4 u
= 4 x 60
= 240

Answer(s): 240