60 stickers are in 3 packets.
The third packet has 3 times as many stickers as the second packet.
The first packet is 10 less than the second packet.
How many less stickers are there in the second packet and the first packet than in the third packet?
Choose the packet with the least stickers to be 1 u.

Number of stickers in the first packet = 1 u
Number of stickers in the second packet = 1 u + 10
Number of stickers in the third packet = 3 x (1 u + 10) = 3 u + 30

Total number of stickers
= 3 u + 30 + 1 u + 10 + 1 u
= 3 u + 1 u + 1 u + 30 + 10
= 5 u + 40

5 u + 40 = 60
5 u = 60 - 40
5 u = 20

1 u = 20 ÷ 5 = 4

Number of less stickers in the second packet and first packet than the third packet
= (3 u + 30) - (1 u + 10 + 1 u)
= (3 u + 30) - (2 u + 10)
= 3 u - 2 u  + 30 - 10
= 1 u + 20
= 1 x 4 + 20
= 4 + 20
= 24

Answer(s): 24