The mass of 4 children, Tammy, Raeann, Gabriel and Ahmad were taken. Only 3 children can be weighed at one time. Tammy, Raeann and Gabriel weighed a total of 82 kg. Raeann, Gabriel and Ahmad weighed a total of 107 kg. Tammy, Gabriel and Ahmad weighed a total of 80 kg. Tammy, Raeann, and Ahmad weighed a total of 127 kg. What is the average mass of the 4 children?
Tammy + Raeann + Gabriel = 82 --- (1)
Raeann + Gabriel + Ahmad = 107 --- (2)
Tammy + Gabriel + Ahmad = 80 --- (3)
Tammy + Raeann + Ahmad = 127 --- (4)

(1) + (2) + (3) + (4)
3(Tammy + Raeann + Gabriel + Ahmad) = 82 + 107 + 80 + 127
3(Tammy + Raeann + Gabriel + Ahmad) = 396
Tammy + Raeann + Gabriel + Ahmad = 396 ÷ 3 = 132

Total mass of the 4 children = 132

Average mass of the 4 children
= 132 ÷ 4
= 33

Answer(s): 33 kg