The students' math homework "Decomposition and Combination" was written in a mess, and the situation they mastered was not as good as I expected. You can choose a way that is conducive to children's understanding and make corresponding metaphors. You can do this:

Compare the decomposed symbol ""to a writer. There are mothers and children in the family, and the mother is gone. The children form a group to find their mothers and add them. The children left their mother and were separated by subtraction. I didn't expect the effect to be good, and the child mastered it easily. Even children who don't usually understand are fine. It seems that teaching mathematics well not only tests teachers' professional knowledge level, but also tests teachers' ability to integrate theory with practice!