Answer:
His son is 10 years old.
Explanation:
Now Aaron's son is s years old, and Aaron is 3s years old.
In 10 years, Aaron's son will be s + 10 years old, and Aaron will be 3s + 10 years old.
In 10 years, Aaron's age will be twice the son's age.
3s + 10 = 2(s + 10)
3s + 10 = 2s + 20
s = 10
His son is 10 years old.