The mass of 4 children, Risa, Jade, Simon and Valen were taken. Only 3 children can be weighed at one time. Risa, Jade and Simon weighed a total of 146 kg. Jade, Simon and Valen weighed a total of 92 kg. Risa, Simon and Valen weighed a total of 50 kg. Risa, Jade, and Valen weighed a total of 60 kg. What is the average mass of the 4 children?
Risa + Jade + Simon = 146 --- (1)
Jade + Simon + Valen = 92 --- (2)
Risa + Simon + Valen = 50 --- (3)
Risa + Jade + Valen = 60 --- (4)

(1) + (2) + (3) + (4)
3(Risa + Jade + Simon + Valen) = 146 + 92 + 50 + 60
3(Risa + Jade + Simon + Valen) = 348
Risa + Jade + Simon + Valen = 348 ÷ 3 = 116

Total mass of the 4 children = 116

Average mass of the 4 children
= 116 ÷ 4
= 29

Answer(s): 29 kg