Final answer:
The weight of the child is 40 pounds, the weight of the father is 200 pounds, and the weight of the mother is 150 pounds.
Step-by-step explanation:
Let's assume the weight of the child is x pounds. According to the given information, the father weighs 5 times as much as the child, so the weight of the father is 5x pounds. The mother weighs 3/4 as much as the father, so the weight of the mother is (3/4)*(5x) = (15/4)x pounds.
The total weight of the family is 390 pounds, so we can write the equation:
x + 5x + (15/4)x = 390
Simplifying the equation:
(4x + 20x + 15x)/4 = 390
39x/4 = 390
Multiplying both sides by 4/39 to solve for x:
x = 40
Therefore, the weight of the child is x = 40 pounds. The weight of the father is 5x = 5*40 = 200 pounds. The weight of the mother is (15/4)x = (15/4)*40 = 150 pounds.