A box contains 4 white 3 red and 4 black marbles One marble

A box contains 4 white, 3 red, and 4 black marbles. One marble is chosen at random, and it is not black. Find the probability that it is white. (Enter your answer as a fraction.)

Solution

There are 4+3 = 7 marbles that are not black.

Of which, 4 are white.

Thus,

P(white|not black) = 4/7 [ANSWER]