Ethan, Samantha, Sebastian and Jayden share the same hobby of collecting stickers. The average number of stickers collected by the 4 friends is 21. Samantha collected 7 more stickers than Sebastian but 12 fewer stickers than Ethan. Jayden collected 2 stickers fewer than Sebastian. Find the average number of stickers collected by Samantha and Jayden. Round off your answer to the nearest whole number.
Number of stickers Sebastian collected = 1 u
Number of stickers Samantha collected = 1 u + 7
Number of stickers Ethan collected = 1 u + 7 + 12 = 1 u + 19
Number of stickers Jayden collected = 1 u - 2

Total number of stickers collected
= 4 x 21
= 84

Total number of stickers collected in units
= 1 u + 1 u + 7 + 1 u + 19 + 1 u - 2
= 4 u + 24

4 u + 24 = 84
4 u = 84 - 24 = 60

1 u = 60 ÷ 4 = 15

Total number of stickers collected by Samantha and Jayden
= 1 u + 7 + 1 u - 2
= 2 u + 5
= 2 x 15 + 5
= 35

Average number of stickers collected by Samantha and Jayden
= 35 ÷ 2
≈ 18 (Round off to the nearest whole number.)

Answer(s): 18