I was in the same position as you are, but I was weak in verbal and strong in math. My suggestion to you is to start off with the Manhattan Number Properties
book (~$15). This book is great for small issues in arithmetic and will teach you helpful hints to help you remember basic concepts (odd + odd = even and odd x odd = odd) I would do about an hour to two hours every night after work until you have completed the book, then I would retest to see how your math score has improved.
Hope this helps.