The present age of a man is four times that of his son. In five years, the man’s age will be three times that of his son. Find the present age of the son?

9 years

10 years

12 years

None of these

Let the son's present age be x.

The man's present age = 4x

In 5 years:

Son's age = x + 5

Man's age = 4x + 5

According to the problem:

4x + 5 = 3(x + 5)

4x + 5 = 3x + 15

4x - 3x = 15 - 5

x = 10