At present, a father is 30 years older than his son. In 12 years, the father will be three times as old as his son. What is the present age of the son?
3 years
Let the present age of the son be \(s\) years. Then the father's present age is \(s + 30\) years.
In 12 years: son's age \(= s + 12\), father's age \(= s + 42\).
Condition: \(s + 42 = 3(s + 12)\).
Expanding: \(s + 42 = 3s + 36\).
\(42 - 36 = 3s - s\), so \(2s = 6\), giving \(s = 3\).
Hence, the present age of the son is 3 years.