Christian, Abigail, Evan and Lucas share the same hobby of collecting marbles. The average number of marbles collected by the 4 friends is 24. Abigail collected 8 more marbles than Evan but 16 fewer marbles than Christian. Lucas collected 4 marbles fewer than Evan. Find the average number of marbles collected by Abigail, Evan and Lucas. Round off your answer to the nearest whole number.
Number of marbles Evan collected = 1 u
Number of marbles Abigail collected = 1 u + 8
Number of marbles Christian collected = 1 u + 8 + 16 = 1 u + 24
Number of marbles Lucas collected = 1 u - 4

Total number of marbles collected
= 4 x 24
= 96

Total number of marbles collected in units
= 1 u + 1 u + 8 + 1 u + 24 + 1 u - 4
= 4 u + 28

4 u + 28 = 96
4 u = 96 - 28 = 68

1 u = 68 ÷ 4 = 17

Total number of marbles collected by Abigail, Evan and Lucas
= 1 u + 8 + 1 u + 1 u - 4
= 3 u + 4
= 3 x 17 + 4
= 55

Average number of marbles collected by Abigail, Evan and Lucas
= 55 ÷ 3
≈ 18 (Round off to the nearest whole number.)

Answer(s): 18