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In all, there are 3 + 4 + 2 + 1 = 10 marbles initially in the basket.
(a) What is the probability that he chooses either a red or the black marble?
P = P(a read) + P(the black) = + = = 0.4.
(b) P = P(1st is a red)*P(2nd is a white) + P(1st is a white)*(P(2nd is a red) = + = = = .
(c) I can not answer this question,
because from the post, it is unclear, if it relates to choosing/pickaping one or two marbles.
While experiment is described accurately in cases (a) and (b), it is not described accurately in case (c).