The mass of 4 children, Nicole, Vanessa, Ben and Andy were taken. Only 3 children can be weighed at one time. Nicole, Vanessa and Ben weighed a total of 92 kg. Vanessa, Ben and Andy weighed a total of 51 kg. Nicole, Ben and Andy weighed a total of 75 kg. Nicole, Vanessa, and Andy weighed a total of 106 kg. What is the average mass of the 4 children?
Nicole + Vanessa + Ben = 92 --- (1)
Vanessa + Ben + Andy = 51 --- (2)
Nicole + Ben + Andy = 75 --- (3)
Nicole + Vanessa + Andy = 106 --- (4)

(1) + (2) + (3) + (4)
3(Nicole + Vanessa + Ben + Andy) = 92 + 51 + 75 + 106
3(Nicole + Vanessa + Ben + Andy) = 324
Nicole + Vanessa + Ben + Andy = 324 ÷ 3 = 108

Total mass of the 4 children = 108

Average mass of the 4 children
= 108 ÷ 4
= 27

Answer(s): 27 kg