HELP!! Struggling with Calculations (PNN Calculation) Sufficient?

I'm using the PNN to study for NAPLEX ive been out of school for 2 years. I wanted to know if the PNN calculation good enough. Im really struggling with the math portion and im so embarrassed and annoyed at myself. i used to be so good at math. my exam is in 5 weeks and im struggling is there a better math resource.