It's weird, because I can do basic math in my head. I rarely use a calculator. But I can't really hold numbers in my head, so it's slow mental calculations as I make sure that I read the numbers correctly and have them in the right places.
I just transpose numbers, putting them in the wrong order. And then when letters are tossed in, or the symbols (less than and greater than were the absolute bane of my first-grade year), then everything gets confusing.
Geometry was fun, though! That was the only math class I ever passed.