Farmer Archie has 4 rabbits. The mass of Rabbit W is the same as the average mass of the 4 rabbits. Rabbit X weighs 2 kg less than the average mass of the 4 rabbits. The mass of Rabbit Y is 10 kg more than the average mass of the 4 rabbits. The mass of Rabbit Z is 8 kg. Find the total mass of the 4 rabbits.
Let 1 u be the average mass of each rabbit.

Total mass of 4 rabbits
= 4 x 1 u
= 4 u

Mass of Rabbit W = 1 u
Mass of Rabbit X = 1 u - 2
Mass of Rabbit Y = 1 u + 10
Mass of Rabbit Z = 8 kg

Total mass of the 4 rabbits
= 1 u + (1 u - 2) + (1 u + 10) + 8 
= 3 u - 2 + 10 + 8
= 3 u + 16

4 u = 3 u + 16
4 u - 3 u = 16

1 u = 16

Total mass of the 4 rabbits
= 4 u
= 4 x 16
= 64 kg

Answer(s): 64 kg