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

Given, ten years ago, a father was twelve times as old as his son and ten years hence, he will be twice as old as his son will be then.

⇒ a – 10 = 12(b – 10)

⇒ a = 12b + 110 ------ (1)

Also, a + 10 = 2(b + 10)

⇒ a = 2b + 10 ------- (2)

Equating eq1 and eq2.

⇒ 12b + 110 = 2b + 10

⇒ b = 10

Thus, a = 30