A father is 30 years older than his son. In ten years times he will be three times as old as his son. Calculate the present age of each one
Let F = father's current age
Let S = son's current age
Then,
F = S + 30 (A father is 30 years older than his son)
Now add on 10 years, giving
F + 10 = 3(S + 10) (In ten years times he will be three times as old as his son.)
Substituting for F = S + 30,
(S + 30) + 10 = 3(S + 10)
S + 40 = 3S + 30
10 = 2S
S = 5, F = 35