Question 908972
let f = the age of the present age of the father
let s = the age of the son
let d = the age of the daughter
:
Write an equation for each statement.
:
The Age Of A Father Is Three Times the age of his son,
f = 3s
 and two times the age of his daughter.
f = 2d
 In eight years the age of the daughter will be twice the age of the son.
d + 8 = 2(s+8)
d + 8 = 2s + 16
d = 2s + 16 - 8
d = 2s + 8
:
f = f therefore,from the 1st two equations we know 
2d = 3s
d = {{{3/2}}}s
d = 1.5s
Back to the last equation, find s, replace d with 1.5s
1.5s = 2s + 8
now this doesn't make sense, there is a major flaw in this problem.
Daughter is 1.5 time the age of the son now, cannot be twice as old in the future!