I am a junior high school math teacher myself. There are two situations you said. The first kind of students have a poor foundation in elementary school mathematics, at least they can't even add or subtract scores. If you are such a person, I suggest you go to the fifth grade of primary school to review the exercises of adding and subtracting fractions. The second is to attend classes without doing any exercises after class. I understand it in class and return it to the teacher after class. If this is the case with you, you will do more exercises.