small math question <we hope>

[shutupndeal]

I may have asked this BUT if I did I cant find it anywhere and this is the only place this question really belongs and at least I know where to find it now so..........

I was trying to find out something the other day and I had one of those totally foggy days where I actually broke out a deck of cards and STILL wasnt sure I was correct, this was my problem. I want to know just how the formula would be written to show this probability example.

What are the odds of me catching 2 spades on the flop if I have the ace and queen of spades on my hand preflop?
I was getting 20-1 but it doesnt seen correct so Id like to see it written. Also if I wanted to figure the exact odds of only one spade falling or all 3 how would that be done? I did so well in statistics in school I cant believe my mind is this rotted! : ) Anyone ever check out that "Holdem" odds book, what kinda stuff is in that?