Let the present age of father be ‘a’ and present age of son be b.

Given, father is three times as old as his son. In 12 years time, he will be twice as old as hi son.

⇒ a = 3b and

a + 12 = 2(b + 12)

⇒ 3b + 12 = 2b + 24

⇒ b = 12

Thus, a = 36