Answer:
4/15
Explanation:
There are 6 white+4black = 10 marbles in the bag
P (white) = white marbles / total marbles = 6/10 = 3/5
We keep the marble
There are 5 white+4black = 9 marbles in the bag
P (black) = black/total = 4/9
P(white, black no replacement) = 3/5 * 4/9 = 3/9 *4/5 = 1/3*4/5 = 4/15