I can't seem to get the rules for the equations in my head how do I memorize it
I'd suggest just doing sums until you can just do the rules automatically or make up a rhyme or a story to get them stuck in your head.
You do understand that you don't actually need to learn off the formulas you just need to know how to do them properly. You are allowed to look up the formulas in your log books on the day.
No problem, i would recommend just looking through the log book before hand to familiarize yourself with where certain formulas are so that your not frustrated trying to look for a certain one on the day. Good luck :)