Andrew, Dylan, Samantha and Elizabeth share the same hobby of collecting cards. The average number of cards collected by the 4 friends is 27. Dylan collected 7 more cards than Samantha but 17 fewer cards than Andrew. Elizabeth collected 3 cards fewer than Samantha. Find the average number of cards collected by Dylan, Samantha and Elizabeth. Round off your answer to the nearest whole number.
Number of cards Samantha collected = 1 u
Number of cards Dylan collected = 1 u + 7
Number of cards Andrew collected = 1 u + 7 + 17 = 1 u + 24
Number of cards Elizabeth collected = 1 u - 3

Total number of cards collected
= 4 x 27
= 108

Total number of cards collected in units
= 1 u + 1 u + 7 + 1 u + 24 + 1 u - 3
= 4 u + 28

4 u + 28 = 108
4 u = 108 - 28 = 80

1 u = 80 ÷ 4 = 20

Total number of cards collected by Dylan, Samantha and Elizabeth
= 1 u + 7 + 1 u + 1 u - 3
= 3 u + 4
= 3 x 20 + 4
= 64

Average number of cards collected by Dylan, Samantha and Elizabeth
= 64 ÷ 3
≈ 21 (Round off to the nearest whole number.)

Answer(s): 21