To learn mathematics well, it is necessary to do more problems, not to mention the tactics of doing problems, but also to do more problems, which is necessary to cultivate mathematical thinking. Don't be afraid, if you don't contact for such a long time, you will inevitably be unfamiliar. It may take a long time to do a problem, but as long as you persist, it will improve the speed of solving problems after a long time. Usually, we must accumulate more different types of problems, so that even if we encounter new problems, we can use our usual experience to solve them unconsciously. Really, I used to be average at math. With persistence and methods, my math scores improved rapidly.