Josiah, Andrew, Levi and Oliver share the same hobby of collecting buttons. The average number of buttons collected by the 4 friends is 30. Andrew collected 9 more buttons than Levi but 16 fewer buttons than Josiah. Oliver collected 2 buttons fewer than Levi. Find the average number of buttons collected by Andrew, Levi and Oliver. Round off your answer to the nearest whole number.
Number of buttons Levi collected = 1 u
Number of buttons Andrew collected = 1 u + 9
Number of buttons Josiah collected = 1 u + 9 + 16 = 1 u + 25
Number of buttons Oliver collected = 1 u - 2

Total number of buttons collected
= 4 x 30
= 120

Total number of buttons collected in units
= 1 u + 1 u + 9 + 1 u + 25 + 1 u - 2
= 4 u + 32

4 u + 32 = 120
4 u = 120 - 32 = 88

1 u = 88 ÷ 4 = 22

Total number of buttons collected by Andrew, Levi and Oliver
= 1 u + 9 + 1 u + 1 u - 2
= 3 u + 7
= 3 x 22 + 7
= 73

Average number of buttons collected by Andrew, Levi and Oliver
= 73 ÷ 3
≈ 24 (Round off to the nearest whole number.)

Answer(s): 24