Yes. I am studying for the NET, the Nelson-Denny, and the GRE. You just do it. You work hard and plod through them all, in the order that you are taking them. A good approach is to break down in bits the elements you need to learn or brush up on. For example, write out a list. On the list might be 1) Review basic multiplication 2) Review basic division 3) Practice reading comprehension
This way you can cross off each item as you complete it. It feels better, and you can see yourself making organized progress.
I know it's frustrating. I have to memorize my multiplication tables for basic math. I never did that it 3rd grade because I was home schooled and my idiot parents just didn't bother.
Work hard!