Make sure that you do all of the homework problems. In fact, if there is a certain type of problem that you still feel that you are unsure about after doing the assigned problems, you should be sure to talk to your TA or go to your professor during his or her office hours to clear up any confusion. Try doing some extra problems. Mathematics classes typically build on previously covered concepts so that it is important to understand things while they are being covered. Also, if you can't do the problems when you have the book to look at, it is unlikely that you will be able to do them in the pressure of a test.
Most students find mathematics texts difficult to read.
Even advanced students find it easier to learn new concepts when someone is there to tell them about it and can immediately answer their questions. He or she can evaluate where you stand in the class and can often give you pointers about what you need to change to do better on the tests. Talk to your professor or your TA about the test so that you understand where you went wrong. If you do decide to drop the class, you should be sure to talk with a college advisor so that you are aware of the consequences for your general program of study. If you are a math major, you should also consult the Math advisor so that you are aware of the consequences to your major.