It's not 15% it's $15

I am unsure of the problem/question you are asking. However, 15% is equivalent to 0.15. If you're asking what 15% of 15 is, you just multiply 0.15 (15) and that results in 2.25. So, $2.25 is the answer ... ?

Did you just add an answer too a question? 15% is 0.15