Question

A ball is drawn from a box containing 5 red, 8 black and 7 blue balls. Determine the probability that:
a) if a ball is drawn at random, it is black.
b) if two balls are drawn, they are both black.
c) if three balls are drawn, exactly one is black, one is blue and one is red.
d) if three balls are drawn, at least one is black.
e) if four balls are drawn, at most one of them is black.
All selection is without replacement.

Answer 1

a 8/20=2/5

Answer 2

b. (8/20)*(7/19)

Answer 3

what is the answer for part c and d
and could you please explain how you got those answers.