The ages of father and son differ by 15 years. 5 years ago the father was 2 times old as his son. Find their present ages.

Correct option is A

Given:
The ages of father and son differ by 15 years.

5 years ago the father was 2 times old as his son.

Solution:

Let's assume that the present age of the son = x,

then the present age of the father = (x + 15).
5 years ago, the father and son's ages would have been (x + 15 - 5) = (x + 10) and (x - 5) respectively.
Now, according to the question,
(x + 10) = 2 × (x - 5)
=> x + 10 = 2x - 10
=> x = 20
So, the present age of the father = (20 + 15) = 35 years and the son = 20 years.