Decimal method is a subtraction calculation method, that is, when the number of units is not enough, subtract the subtraction with 10 and add the remainder to the number of units. For example, 13-7, first divide 13 by 10 and 3, then subtract 7 from 10 to get 3, and add the obtained 3 to the minuend 3 to get 6.

The method of breaking ten is also called "borrowing ten", which is a calculation method used in the subtraction of abdication within 20. By using the method of breaking ten, the abdication subtraction within 20 can be transformed into the addition and subtraction within 10 that students are familiar with, thus making simplification difficult.

Example:

When calculating 13 minus 7, considering that unit 3 minus 7 is not enough, we borrow 10 from ten digits to subtract it, and subtract 7 from 10 to get 3, and then add 3 to unit 3 to equal 6. This is a ten-way break.