Administrative assistant

jose, paul and dan went fishing and all three of them caught a fish dan's fish weighed four times as much as paul,s fish and jose,s fish weigh half as much as dan,s fish altogether the three fish weighed 21 pounds. how much did each fish weigh?

Let x be Jose's weight
Let y be Paul's weight
Let z be Dan's weight

x + y + z = 21 (Equation #1)
z = 4*y, so y = z/4 (Equation #2)
x = (1/2)z = z/2 (Equation #3)


Replace (Equation #2) and (Equation #3) in (Equation #1)
z/2 + z/4 + z = 21
2z/4 + z/4 + 4z/4 = 21
7z/4 = 21
(4/7)* 7z/4 = 21 * 4/7
z = 84/7 = 12
x = z/2 = 12/2 = 6
y = z/4 = 12/4 = 3