Students must have an understanding of basic subtraction and place value in order to be successful with borrowing.
1. Introduce using base 10 blocks.
Example:
24
-16
2. Model 24 using 2 longs, and 4 cubes; and 16 using 1 long and 6 cubes.
3. Show how there are not enough cubes to take 6 away from 4. So exchange a long(10) for 10 cubes. Now there are 14 cubes - 6 cubes in the ones place. Subtract 14 - 6=8.
4. Complete 14-6 and identify that there is only 1 long left from 24, so subtract your numbers in the tens place1 - 1=0.
5. Note the check! If you add 8 to 16, then the answer will be 24.