hold em odds questions

[rheaume]

got a couple math question to help me get a better grasp on "on the fly" hold em odds.

* heads up in an SNG. you're dealt 2 rags. what are the odds your opponent has at least one ace? how do you calculate that?

* there's a flop of AAA. now how do you do that math? what if you're not heads up, what if there are 5 people in the hand?

* same question above, but with 2 aces instead of 3 ex. AA3

thanks for your help