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

Number of stickers in the third packet = 1 u
Number of stickers in the second packet = 1 u + 10
Number of stickers in the first 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 = 70
5 u = 70 - 40
5 u = 30

1 u = 30 ÷ 5 = 6

Number of less stickers in the second packet and third packet than the first 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 6 + 20
= 6 + 20
= 26

Answer(s): 26