SOLUTION
The bag contains the following marbles
2 red, 1 white and 1 blue.
(a) Sample space means listing all the possible outcomes, which is done thus:
Since two marbles are usually picked. It is either we pick
2 red marbles or
1 red and 1 white
1 red and 1 blue
1 white and 1 blue.
Hence the sample space is
2 red marbles
1 red and 1 white
1 red and 1 blue
1 white and 1 blue.
(b) The probability of selecting at least one red marble
The probability of selecting at least 1 red marble is
1 - probability of selecting no red marble

Now from what we have above
2 red marbles or
1 red and 1 white
1 red and 1 blue
1 white and 1 blue
It means that the total sample space is 4, that is 4 possible outcomes.
Not picking red means picking 1 white and 1 blue (that is 1 outcome)
Hence probability of no red is

The probability of selecting at least 1 red marble becomes

The complement of this event that is (the probability of selecting at least 1 red marble is) is the probability of selecting no red marble.
We have gotten that initially as
