Dylan, Luke, Sophia and Jacob share the same hobby of collecting buttons. The average number of buttons collected by the 4 friends is 22. Luke collected 6 more buttons than Sophia but 15 fewer buttons than Dylan. Jacob collected 3 buttons fewer than Sophia. Find the average number of buttons collected by Luke and Jacob. Round off your answer to the nearest whole number.
Number of buttons Sophia collected = 1 u
Number of buttons Luke collected = 1 u + 6
Number of buttons Dylan collected = 1 u + 6 + 15 = 1 u + 21
Number of buttons Jacob collected = 1 u - 3

Total number of buttons collected
= 4 x 22
= 88

Total number of buttons collected in units
= 1 u + 1 u + 6 + 1 u + 21 + 1 u - 3
= 4 u + 24

4 u + 24 = 88
4 u = 88 - 24 = 64

1 u = 64 ÷ 4 = 16

Total number of buttons collected by Luke and Jacob
= 1 u + 6 + 1 u - 3
= 2 u + 3
= 2 x 16 + 3
= 35

Average number of buttons collected by Luke and Jacob
= 35 ÷ 2
≈ 18 (Round off to the nearest whole number.)

Answer(s): 18