This is the first half of a two-part article on how to do poker probability problems using combinations of cards, with the difficult math done by something called a combinations calculator. I spent far longer writing this one than most of my PN contributions, and I'm really pleased with the result. If you follow along and do the work with me, rather than just blast through it as fast as your eyeballs can scan the words, you'll go from knowing nothing about this kind of calculation to being able to pose and answer complex poker-math problems on your own. I owe a giant thanks to five blog readers who responded to my plea in the previous post, and took considerable time and effort to proofread my first draft. Between them, they found six mistakes, ranging from trivial to huge. Without their help in advance, I would now have to spend the next few days being embarrassed and submitting corrections as PokerNews readers pointed out my mistakes. But due to their careful scrutiny, I'...