Professor Homunculus sez:

That’s probably a good thing, because you won’t have to unlearn the right-to-left way they teach you to do subtraction in schools. It is pretty lame. If you want a way to do fast mental subtraction, just as easy as they do it with pencil and paper in school, check out:

http://mathmojo.com/basic_oper.....ction.html

For a very clear and easy way to understand regrouping in general, try:

http://mathmojo.com/interestin.....rying.html

I hope this helped. Let me know how you do,

- Prof. Hunc