Favorite/Underdog

[Apocalypse]

In "Winning Low-Limit Hold-em" by Lee Jones there is an introductary passage of playing the flop. He gives the following example:

You hold: As Ks

Your opponent holds: 8c 7d

On these flops there are various odds:

Before the flop : you are 2:1 favorite
Flop is Qd 9h 2c : you are 3:1 favorite
Flop is Qd 8h 2c : he is a 3.2 :1 favorite
Flop is Qd 8s 2c : he is a 2.5 :1 favorite
Flop is Qs 8s 2c : you are even money (1:1)
Flop is Ad 6h 2h: you are a 15:1 favorite
Flop is Ad 8h 4c: you are a 4:1 favorite
Flop is Qd 8h 7c: you are a 19:1 favorite
Flop is Ad Kc 2h: you are a 164:1 favorite

My question is actually really simple: what are the calculations behind this?? I tried some stuff, but it never gave the results presented here. If someone would have the kindness of showing how its done (especially the even money thing), id greatly appreciate it. Thanks! [img]/images/graemlins/smile.gif[/img]