The mass of 4 children, Victoria, Lynn, Gabriel and Justin were taken. Only 3 children can be weighed at one time. Victoria, Lynn and Gabriel weighed a total of 148 kg. Lynn, Gabriel and Justin weighed a total of 63 kg. Victoria, Gabriel and Justin weighed a total of 52 kg. Victoria, Lynn, and Justin weighed a total of 109 kg. What is the average mass of the 4 children?
Victoria + Lynn + Gabriel = 148 --- (1)
Lynn + Gabriel + Justin = 63 --- (2)
Victoria + Gabriel + Justin = 52 --- (3)
Victoria + Lynn + Justin = 109 --- (4)

(1) + (2) + (3) + (4)
3(Victoria + Lynn + Gabriel + Justin) = 148 + 63 + 52 + 109
3(Victoria + Lynn + Gabriel + Justin) = 372
Victoria + Lynn + Gabriel + Justin = 372 ÷ 3 = 124

Total mass of the 4 children = 124

Average mass of the 4 children
= 124 ÷ 4
= 31

Answer(s): 31 kg