The essence of the ten-break method is to solve the problem that a two-digit number from 10 to 20 subtracts another number within 10.

For example, 17-9=

Step 1: 17 minus 9 digits is not enough, so use 10 digits to supplement it. Divide 17 into 10+7. Left 7, right 10.

Step 2: 10 minus negative 9 equals 1, and write it at the bottom of 10.

Step 3: Add the remaining 7 and the reduced 1 to 8 to get the final result.

Reference materials? You can refer to the formula of breaking ten methods in the first book of mathematics in grade one:

Breaking the ten laws is simple;

A dozen MINUS 9, plus1; A dozen MINUS 8, a few plus 2; A dozen MINUS seven, a few plus three; A dozen MINUS six, a few plus four; A dozen MINUS five, a few plus five;

A dozen MINUS four, a few plus six; A dozen MINUS three, a few plus seven; A dozen MINUS two, a few plus eight; A dozen MINUS 1, a few plus 9.