There are a total of 4 outcomes that involve choosing a blue marble
Here, we want to write a sample space for the selection
For us to have the sample space, we will have to write out the possible outcomes
We shall be representing the blue marble by b, the green by g and the yellow by y
We have the sample space as follows;
{1B,1G,1Y,2B,2G,2Y,3B,3G,3Y,4B,4G,4Y}
From the sample space, we can see that there are actually 12 possible results
Now, to get the outcomes involving blue marbles, we simply select the members of the sample space having B at the back
We have these as 1B, 2B, 3B and 4B
This is a total of 4 outcomes