Subtraction by "Regrouping"
(Also called "borrowing" or "trading")
To subtract numbers with more than one digit:

write down the larger number first and the smaller number directly below it
making sure to line up the columns!
 then do subtractions one column at a time like this (press play button):
Smaller Number  Bigger Number
But what if a column has a smaller number on the top? How do you do 2  5 ? 

The Solution: 
Make the "2" larger by "regrouping" like this (press play button): 
In 32:
So you:

And this is how to do it:
You can use this method whenever a column has a smaller number on top, as in this example:
Zero
But you can't regroup from zero ...
But you can make a "0" into a "10" by regrouping it first, them carry on normally, like this:
Now, you can practice with these Subtraction Worksheets