The mass of 4 children, Emily, Gabby, George and Ryan were taken. Only 3 children can be weighed at one time. Emily, Gabby and George weighed a total of 47 kg. Gabby, George and Ryan weighed a total of 57 kg. Emily, George and Ryan weighed a total of 75 kg. Emily, Gabby, and Ryan weighed a total of 85 kg. What is the average mass of the 4 children?
Emily + Gabby + George = 47 --- (1)
Gabby + George + Ryan = 57 --- (2)
Emily + George + Ryan = 75 --- (3)
Emily + Gabby + Ryan = 85 --- (4)

(1) + (2) + (3) + (4)
3(Emily + Gabby + George + Ryan) = 47 + 57 + 75 + 85
3(Emily + Gabby + George + Ryan) = 264
Emily + Gabby + George + Ryan = 264 ÷ 3 = 88

Total mass of the 4 children = 88

Average mass of the 4 children
= 88 ÷ 4
= 22

Answer(s): 22 kg