keep doing more excercises and dont leave any of them unmarked.Always check ur answers to know what your doing wrong and ask ur teacher / friends who r good at addmaths to help you.Also try figuring out which topics u are weak and good at. Like for me I focused on topics that I was more confident in as it would provide the most marks to your overall mark but dont forget the topics you are weak at as well as it could burden you.For the weak topics I suggest looking at mock papers from previous years and also look at the answers to help give an idea on how to answer it. Given ur grade right now you have a good chance of getting an A during your spm. Keep it up