Answer:
3/50
Step-by-step explanation:
There are 5 + 4 + 2 + 6 + 3 = 20 marbles in the bag
P(draw a black) = 6/20 = 3/10
If the black marble is replaced, then there are 20 marbles in the bag again.
P(draw a blue) = 4/20 = 1/5
P(draw a black and blue with replacement) = (3/10)(1/5) = 3/50
