Farmer Luke has 4 roosters. The mass of Rooster Q is the same as the average mass of the 4 roosters. Rooster R weighs 4 kg less than the average mass of the 4 roosters. The mass of Rooster S is 5 kg more than the average mass of the 4 roosters. The mass of Rooster T is 14 kg. Find the total mass of the 4 roosters.
Let 1 u be the average mass of each rooster.

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

Mass of Rooster Q = 1 u
Mass of Rooster R = 1 u - 4
Mass of Rooster S = 1 u + 5
Mass of Rooster T = 14 kg

Total mass of the 4 roosters
= 1 u + (1 u - 4) + (1 u + 5) + 14 
= 3 u - 4 + 5 + 14
= 3 u + 15

4 u = 3 u + 15
4 u - 3 u = 15

1 u = 15

Total mass of the 4 roosters
= 4 u
= 4 x 15
= 60 kg

Answer(s): 60 kg