The sum of the ages of a son and his father is 56 years. After four years, the father's age will be three times the son's age. Find the son's present age.

Explanation

Let the son's present age be x years. Then the father's present age is 56 − x years.

After 4 years, their ages will be x + 4 and 60 − x. Therefore,

60 − x = 3(x + 4)
60 − x = 3x + 12
48 = 4x
x = 12

Hence, the son's present age is 12 years.