Answer:
His son is 13 years old now.
Explanation:
Since the man was 26 years old when his son was born, his age is 26 more than his son's age, or mathematically speaking, x + 26 if the age of his son is x.
26 + x - dad's age
x - son's age
3 x son's age = dad's age
3x = 26 + x
2x = 26
x = 13
His son is 13 years old.