For the sake of understanding, I divide a dozen into ten and ten, such as 17, and we divide them into 10 and 7. Let's ignore the last few. Take the top ten or ten MINUS eight, for example. It can be divided into ten MINUS eight and a few more. So we can get the final result by adding a few and two.

For example:14-8 =10-8+4 = 4+2 = 6. 16-8= 10-8+6=6+2=8。

This method has a professional name called Breaking Ten Methods.

Extended data:

Decimal method is a calculation method. When the unit is not reduced enough, subtract 10 by subtraction and add the remainder to the number in the unit, that is, the decimal method.

Subtraction by abdication, a special mathematical term, can also be called subtraction by borrowing. That is, when two numbers are subtracted and the number of digits to be subtracted is not enough, borrowing the previous digit is equivalent to adding 10 to this digit, and then calculating.

References:

Baidu encyclopedia-abdication subtraction