Answer:
The weights are 50 lb, 35 lb, and 35 lb.
Explanation:
The three boys weight x, y, and z pounds.
One boy weighs 50 lb, so x = 50. The other 2 boys have the same weight, so y = z.
The average weight is the sum of the three weights divided by 3.
(x + y + z)/3 = 40
(50 + y + y)/3 = 40
2y + 50 = 120
2y = 70
y = 35
z = y = 35
Answer: The weights are 50 lb, 35 lb, and 35 lb.