Question 935173
f = father's present age
s = son's
:
I don't think we have enough information to get a unique solution, anyway
 write an equation for each statement
:
A man is older than his son by 30 years
f = s + 30
 in how many years will the fathers age be twice his sons age?
let y = no. years for this to be true
f + y = 2(s+y)
f + y = 2s + 2y
f = 2s + 2y - y
f = 2s + y
Replace f with s+30
s + 30 = 2s + y
30 = 2s - s + y
30 = s + y
right here you can see there could be many solutions
If s = 20, y = 10, then f = 50
or
s = 10, y = 20, then f = 40
or
s = 5, y = 25, then f = 35