Question

Write three numbers greater 20 that have a 9 as a factor

Answer 1

27, 36, and 45.
Here's a good nines trick.
9
18
27
36
45
If you pay attention is just adds a ten and minuses a 1 from each number.
8,7,6,5. And 1,2,3,4. 
Hope this helps :)

Answer 2

The numbers are 27, 36, and 81