100 stickers are in 3 bags.
The second bag has 3 times as many stickers as the third bag.
The first bag is 20 less than the third bag.
How many less stickers are there in the third bag and the first bag than in the second bag?
Choose the bag with the least stickers to be 1 u.

Number of stickers in the first bag = 1 u
Number of stickers in the third bag = 1 u + 20
Number of stickers in the second bag = 3 x (1 u + 20) = 3 u + 60

Total number of stickers
= 3 u + 60 + 1 u + 20 + 1 u
= 3 u + 1 u + 1 u + 60 + 20
= 5 u + 80

5 u + 80 = 100
5 u = 100 - 80
5 u = 20

1 u = 20 ÷ 5 = 4

Number of less stickers in the third bag and first bag than the second bag
= (3 u + 60) - (1 u + 20 + 1 u)
= (3 u + 60) - (2 u + 20)
= 3 u - 2 u  + 60 - 20
= 1 u + 40
= 1 x 4 + 40
= 4 + 40
= 44

Answer(s): 44