Aaron, Sebastian, Zoey and Ellie share the same hobby of collecting cards. The average number of cards collected by the 4 friends is 22. Sebastian collected 9 more cards than Zoey but 12 fewer cards than Aaron. Ellie collected 2 cards fewer than Zoey. Find the average number of cards collected by Sebastian, Zoey and Ellie. Round off your answer to the nearest whole number.
Number of cards Zoey collected = 1 u
Number of cards Sebastian collected = 1 u + 9
Number of cards Aaron collected = 1 u + 9 + 12 = 1 u + 21
Number of cards Ellie collected = 1 u - 2

Total number of cards collected
= 4 x 22
= 88

Total number of cards collected in units
= 1 u + 1 u + 9 + 1 u + 21 + 1 u - 2
= 4 u + 28

4 u + 28 = 88
4 u = 88 - 28 = 60

1 u = 60 ÷ 4 = 15

Total number of cards collected by Sebastian, Zoey and Ellie
= 1 u + 9 + 1 u + 1 u - 2
= 3 u + 7
= 3 x 15 + 7
= 52

Average number of cards collected by Sebastian, Zoey and Ellie
= 52 ÷ 3
≈ 17 (Round off to the nearest whole number.)

Answer(s): 17