Small stick technique
Prepare some sticks with the children. When teaching children, let them count one by one. By counting sticks, you can intuitively understand the addition and subtraction, and call the baby to count according to the number. I believe that most babies will know twice.
Children's song method
Put these simple addition and subtraction operations into some nursery rhymes and teach your baby to sing over and over again. Nursery rhymes are catchy, and the baby will sing them several times. Moreover, children are naturally interested in songs. I believe it is not difficult to learn addition and subtraction as long as the baby is willing to learn from his parents.
Formula method
Addition and subtraction have corresponding formulas. When teaching children to learn, teach them to recite these formulas directly. I believe the baby will read it after reciting it several times. At the same time, the baby will actually operate subconsciously, at least simply adding and subtracting.
Toy law
Take children one toy after another and learn to add and subtract while playing with toys. In this way, if you play in middle schools and schools, I believe your children will learn better, learn more and remember more. This is typical self-entertainment.