There are 20 9s between 0-100 This includes:
The numbers ending in 9 are: 9, 19, 29, 39, 49, 59, 69, 79, 89, 99.
That's 10
And numbers starting with 9 that is: 90, 91, 92, 93, 94, 95, 96, 97, 98, 99.
Also 10