The current textbooks are all changed in the past, and some of them are changed so that we can't understand them, which is really annoying. I suggest you go to the bookstore to read the corresponding math reference books in the second volume of the first grade of the primary education edition, which may solve your troubles. There are detailed solutions in the resources. Read more books and choose one that you and your children can understand. Hehe, take the children. I wish your children better and better, and their grades are getting better and better. I hope I can help you.