At the start, you have 52 cards. 26 are red and 26 are black. The chances of drawing either a black or red card is 26/52, which is 50%. However, you have drawn 2 black cards already, so now you have 26 red cards and 24 black cards, that's 50 cards. Now all you have to do is figure the probability of drawing another black card, and your chances are 24/50 (reduced is 12/25), or 48%.

At the start, you have 52 cards. 26 are red and 26 are black. The chances of drawing either a black or red card is 26/52, which is 50%. However, you have drawn 2 black cards already, so now you have 26 red cards and 24 black cards, that's 50 cards. Now all you have to do is figure the probability of drawing another black card, and your chances are 24/50 (reduced is 12/25), or 48%.