The required numbers are 6 and 3
Solution: Assume the required numbers are a and b,
Given that the sum of two numbers is nine that is,

One number is three more than the other that is,

On substituting (2) in (1) we get,

On grouping the similar terms we get,


On substituting (3) in (1) we get,

Therefore, the number are 6 and 3.