I'll occasionally make dumb math errors as well.. my advice is to read each question carefully so that you know exactly what they are asking. Sometimes I'll sort of skim a question and end up calculating something other than the answer (ex. calculating how much a container is filled vs. how much more room is available). Also, write everything down that you can when working on a problem instead of trying to make a bunch of mental notes and write your math work down clearly... my crappy handwriting has messed me up before, haha. I wouldn't be too worried though, I'm sure you'll be on point during the actual test.