There are several methods for using number splitting for subtraction. Many of the structured ones are basically setting the stage for the borrowing algorithm. Funny Numbers are a fun way to get students borrowing that also uses multiple representations. JJ’s method is a little more flexible, but just decomposition again.
One structured approach looks like this:
|Split the minuend and subtrahend on the hundreds, tens, and ones.||As you can’t subtract 7 from 2 and end up with a positive numbers, move ten over.||Subtract tens from tens, units from units.||Put the two pieces of the difference together.|
Some people like to use a chart format.
Another approach is to split the second number.
82 – 37
= 82 – 30 – 7
= 52 – 7
A game from the BBC that probably illustrates decomposition subtraction better than I can.