Answer:
9 and also 3
Explanation:
Numbers whose digits add up to 9 are divisible by 9. For example 18, 27, 36, 45, 54, 63, 72, 81 are all divisible by 9.
Numbers whose digits add up to any number divisible by three are divisible by three. So 237 has a digit sum of 2+3+7= 12. 12 is divisible by three, so 237 is divisible by three.
In this question any number with a digit sum of 9 is divisible by three as well as 9.