18 is 9% of what number? show your work, youu

For me, I use proportion to solve this kind of questions.

18 is 9% of x
Set up your proportion:

18 = 9%
---    
 x  = 100% 

*Since a percent equals 100, you have to put 100% below 9%
*Then cross multiple divide; 100 x 18 / 9 which equals 200

x=200

18 is 9% of 200