i mean written down sums, not mental arithmatic.

i just tried to do a simple "take away" sum and failed miserably. in my head, easy peasy, but written down - uh uh. i can still add up and do do mulitplication, long division however...

can you remind me how to do it? diagrams would help. i.e. we couldnt work out how to do this:

221
-56
_____
= ???