And now let's look at the correct model. If we number all the balls and draw them one after another, then the experiment, as the table shows, will have 16-4=12 equiprobable outcomes (four pairs with equal numbers are excluded).

Let's assume that balls 1 and 2 are black and balls 3 and 4 are white. Then it is easy to single out all the outcomes favorable to our event and make sure that there are 8 of them.