Alan had thrice as many stickers as Yvonne. After Alan and Yvonne had given 40% and 20% of their stickers to Wendy respectively, the number of stickers that Wendy had increased by 1/4. Wendy had 1680 stickers in the end. How many stickers did Yvonne have in the end?

a = 3y

2/5 a + 1/5 y = 1/4 w
5/4 w = 1680
solve all that, and then 4/5 y = 192

number of stickers of Yvonne --- x

number of stickers for Alan ---- 3x
number of stickers Wendy had at start --- y

Wendy gets:
.4(3x) + .2x = 1.4x
so now she has y + 1.4x
y +1.4x = (5/4)y
1.4x = (1/4)y
7x/5 = y/4
y = 28x/5

also : y + 1.4x = 1680
28x/5 + 1.4x = 1680
7x = 1680
x = 240
y = 28/5(240) = 1344

state your conclusion by subbing in my definitions