50 stickers are in 3 packets.
The 1st packet has 5 times as many stickers as the 2nd packet.
The 3rd packet is 4 times as many stickers as the 2nd packet.
How many less stickers are there in the 2nd packet than in the 1st packet and 3rd packet?
Choose the packet with the least stickers to be 1 u.

Number of stickers in the 2nd packet = 1 u
Number of stickers in the 1st packet = 5 x 1 u = 5 u
Number of stickers in the 3rd packet = 4 x 1 u = 4 u

Total number of stickers
= 1 u + 5 u + 4 u
= 10 u

10 u = 50
1 u = 50 ÷ 10 = 5

Number of stickers less in the 2nd packet than in the 1st and 3rd packets
= Total number of stickers in 1st and 3rd packet - Number of stickers in 2nd packet
= 5 u + 4 u - 1 u
= 8 u 
= 8 x 5
= 40

Answer(s): 40