In the case of the coin, one side is heads and the other is tails. Since all events must equal 1that means that the probability of getting a heads is 1/2 and the probability of getting tails is 1/2.
The bag of marbles contains a total of 9 marbles
Probability so
the probability of drawing a red is 3/9
the probability of drawing a blue is 3/9
the probability of drawing a yellow is 3/9
IF the marbles are replaced after being drawn which is the assumption.
