Tommy bought 25% more stickers than Audrey. William bought 20% fewer stickers than Tommy. Tommy and Audrey gave William some stickers in the ratio 3 : 2. As a result, William had twice as much stickers as before. Given that Audrey had 21 more stickers than Tommy in the end, how much stickers did William receive?

	Tommy	Audrey	William
	5x5	4x5
	5x5		4x5
Before	25 u	20 u	20 u
Change			+ (2 x 20 u) = + 40 u
	- 3x8 = - 24 u	- 2x8 = - 16 u	+ 5x8 =  + 40 u
After	1 u	4 u	60 u

100% + 25% = 125%
125% = ¹²⁵₁₀₀ = ⁵₄

100% - 20% = 80%
80% = ⁸⁰₁₀₀ = ⁴₅

The number of stickers that Tommy had at first is the repeated identity.
LCM of 5 and 5 = 25

The change in the number of stickers that William had is the repeated identity when Tommy and Audrey gave to William.
LCM of 40 and 5 = 40

Number of stickers that Audrey had more than Tommy in the end
= 4 u - 1 u
= 3 u

3 u = 21
1 u = 21 ÷ 3 = 7

Number of stickers that William received
= 24 u + 16 u
= 40 u
= 40 x 7
= 280

Answer(s): 280