180 stickers are in 3 boxes.
The second box has 3 times as many stickers as the third box.
The first box is 40 less than the third box.
How many less stickers are there in the third box and the first box than in the second box?
Choose the box with the least stickers to be 1 u.

Number of stickers in the first box = 1 u
Number of stickers in the third box = 1 u + 40
Number of stickers in the second box = 3 x (1 u + 40) = 3 u + 120

Total number of stickers
= 3 u + 120 + 1 u + 40 + 1 u
= 3 u + 1 u + 1 u + 120 + 40
= 5 u + 160

5 u + 160 = 180
5 u = 180 - 160
5 u = 20

1 u = 20 ÷ 5 = 4

Number of less stickers in the third box and first box than the second box
= (3 u + 120) - (1 u + 40 + 1 u)
= (3 u + 120) - (2 u + 40)
= 3 u - 2 u  + 120 - 40
= 1 u + 80
= 1 x 4 + 80
= 4 + 80
= 84

Answer(s): 84