No, it isn't allowed in the exam. Better off to box the answer, then put a single cross through it. So the examiner can read it, and award you marks just in case you get it wrong(if it maths for working out)
I think it's strictly forbidden, the supervisor will give a 10min lecture of what you can or can not do at the beginning of each exam anyway to clarify
lol me and my friend accidentally ended up using it in the English exam, because we didn't know. You're not supposed to use it, but if you accidentally do you won't lose any marks