Question

What is 9/10 as a percentage

Answer 1

To transfer a faction to a percent like this we can add a 0 to the 10 to make it 100 and a 0 to 9 to make it 90. In this case, the number is simple number rather than a decimal or something else more complicated that you might learn later. 90 of 100 is simplified to simply transferring 90 to 90% of 100 so the same goes for 9/10, 9 is 90% of 10.

Answer 2

9/10 would be 90%

To help you out a little more, it's really easy if the problem is stated like this.
1/10 = 10%
2/10 = 20%
3/10 = 30%
4/10 = 40% 
5/10 = 50%
6/10 = 60%

and so on and so forth...