I think it can be done, as you do get a calculator and it's mainly stuff to do with rearranging equations and then plugging the numbers in. My friend does Chemistry and she isn't great with Maths and she survives but she sometimes makes silly mistakes and loses marks for it. You just have to be prepared to put time aside for working on your maths skills in your A Level, or for finding ways that make sense to you. Also, check everything you do and don't take shortcuts - if you write down all the separate calculations you do, you (or your teacher or your examiner) will find it easier to understand what you have done and where you have gone wrong