What is the math behind the second card trick?

To put it simply, the deck has 52 cards (minus jokers). Of those 52, there are 4 suites. Two of them are red, two of them are black. Because each suite has an equal number of cards, and there are only two colors, 26 of the cards must be black, and the other 26 must be red. When the deck is divided randomly in half; you can count how many of either color card you have, and it will correspond to the opposite color card count the other person has. If I have 14 black cards, the other person has 14 red cards, because out of my 26 cards, if 14 are black, that means 12 are red, and 26-12=14 which is the number of black cards I have.