The mass of 4 children, Lynn, Gabby, Zane and Japheth were taken. Only 3 children can be weighed at one time. Lynn, Gabby and Zane weighed a total of 130 kg. Gabby, Zane and Japheth weighed a total of 150 kg. Lynn, Zane and Japheth weighed a total of 59 kg. Lynn, Gabby, and Japheth weighed a total of 105 kg. What is the average mass of the 4 children?
Lynn + Gabby + Zane = 130 --- (1)
Gabby + Zane + Japheth = 150 --- (2)
Lynn + Zane + Japheth = 59 --- (3)
Lynn + Gabby + Japheth = 105 --- (4)

(1) + (2) + (3) + (4)
3(Lynn + Gabby + Zane + Japheth) = 130 + 150 + 59 + 105
3(Lynn + Gabby + Zane + Japheth) = 444
Lynn + Gabby + Zane + Japheth = 444 ÷ 3 = 148

Total mass of the 4 children = 148

Average mass of the 4 children
= 148 ÷ 4
= 37

Answer(s): 37 kg