Find a maths teacher you like/get on with and ask them. It doesn't matter if its not your teacher, they can run you through the basics in a spare 10 mins. Do you have any mates/older siblings/parents who understand it a bit better?
I know it might be embarassing now, but you'll realise that its better to ask and get a decent maths grade than to try and save face and struggle on.
If your teacher tries to embarrass you, ask them what the f**k they think they're doing, and if they want to appear to be a good teacher by having a nice % (thats percentage) of people pass the test, you're gonna need all the help they can give.