A man is six time as his son. Twenty years later, the man will be twice as old as his son. find the age of the man when his son was born.

Let the Present Age of his Son be : S

Given the Man is Six times as his Son

⇒ The Present of Age Man is : 6S

Twenty Years Later:

⇒ The Age of his Son will be : S + 20

⇒ The Age of the Man is : 6S + 20

Given : After 20 years, The Man will be Twice as old as his Son

⇒ 2 (S + 20) = 6S + 20

⇒ 2S + 40 = 6S + 20

⇒ 4S = 20

⇒ S = 5

⇒ The Present Age of his Son is : 5

⇒ The Present Age of the Man is : 6S = 6 * 5 = 30

⇒ The Age of Man when his Son was Born is 30 - 5 = 25 years

He was 20 when his son was born.

He was 40 when he was twice as old.