The Probability of 2 Black is 24C2/48C2 (24 black cards choose 2) and 2 Ks is 8C2/48C2 (8 kings choose 2) but the tricky part is that we have to remove all double counting which happens when 2 black kings are picked which happens 4C2/48C2
So the solution should be (24*23 + 8*7 - 4*3)/(48*47)