The mass of 4 children, Marion, Natalie, Ivan and Brandon were taken. Only 3 children can be weighed at one time. Marion, Natalie and Ivan weighed a total of 95 kg. Natalie, Ivan and Brandon weighed a total of 76 kg. Marion, Ivan and Brandon weighed a total of 149 kg. Marion, Natalie, and Brandon weighed a total of 88 kg. What is the average mass of the 4 children?
Marion + Natalie + Ivan = 95 --- (1)
Natalie + Ivan + Brandon = 76 --- (2)
Marion + Ivan + Brandon = 149 --- (3)
Marion + Natalie + Brandon = 88 --- (4)

(1) + (2) + (3) + (4)
3(Marion + Natalie + Ivan + Brandon) = 95 + 76 + 149 + 88
3(Marion + Natalie + Ivan + Brandon) = 408
Marion + Natalie + Ivan + Brandon = 408 ÷ 3 = 136

Total mass of the 4 children = 136

Average mass of the 4 children
= 136 ÷ 4
= 34

Answer(s): 34 kg