The mass of 4 children, Gabby, Joelle, Asher and Paul were taken. Only 3 children can be weighed at one time. Gabby, Joelle and Asher weighed a total of 74 kg. Joelle, Asher and Paul weighed a total of 73 kg. Gabby, Asher and Paul weighed a total of 63 kg. Gabby, Joelle, and Paul weighed a total of 126 kg. What is the average mass of the 4 children?
Gabby + Joelle + Asher = 74 --- (1)
Joelle + Asher + Paul = 73 --- (2)
Gabby + Asher + Paul = 63 --- (3)
Gabby + Joelle + Paul = 126 --- (4)

(1) + (2) + (3) + (4)
3(Gabby + Joelle + Asher + Paul) = 74 + 73 + 63 + 126
3(Gabby + Joelle + Asher + Paul) = 336
Gabby + Joelle + Asher + Paul = 336 ÷ 3 = 112

Total mass of the 4 children = 112

Average mass of the 4 children
= 112 ÷ 4
= 28

Answer(s): 28 kg