If you feel you're lacking basic math skills, it's smart of you to want to do some preparation before beginning your TPR course. I am a TPR GMAT instructor and I can tell you that the class moves at a brisk pace, especially the quant portion.
The best advice is that you talk with your TPR instructor at the very first class and let him/her know where you stand quant-wise. I also suggest that you pick up a copy of TPR's MathSmart book (your teacher might have a copy you can borrow). MathSmart is a great book that will help you with the basics, such as operations with fractions, algebra, translating problem solving questions into math, etc. Also, spend as much time as you need on the first two prework assignments. These prework assignments review math definitions and basic algebra and you will need to understand these topics in order to properly use the techniques you will learn.
Also, consider signing up for a class or two at a community college. It can help you on the GMAT and you will need some review before you start b-school anyway.