I'm not great at math either. One has to practice practice practice! Two good books are calculations with confidence (cheap on half.com) and henke's med-math. We have a dosage exam each semester that one has to obtain a 90% to pass. You only get 1 rewrite, fail that and ur out, so some incentive to study,lol
Its really not that hard, just takes practice and UNDERSTANDING of what is being asked. They (professors) love to throw in a "extra" information and numbers into the question, not so much to confuse you (it can though,lol) but to ensure you understand what is required. On one recent exam, they had this long question, with eventually 75cc/hr in the question and how would you set up the pump? ans 75 ml/hr (1 cc= 1 ml) but some students figured it cant be just 75 ml/hr that's to easy,lol so they dug up some wacky formula and got the question wrong!! Check out the math section in the students forum on here, lots of great advice.