Answer:
The probability is 9/266
Step-by-step explanation:
The first thing to do here is get the total number of marbles = 5 + 7 + 9 = 21 marbles
Now we are drawing the marbles without replacement, this means once a marble is drawn there is a decrease in the total number of marbles left.
The probability of drawing a green marble initially = number of green marbles/ total
number of marbles = 9/21 = 3/7
Now, we want to draw a blue marble
There are 5 blue marbles and we have already drawn one marble from the total. So the probability of drawing a blue marble would be 5/20 = 1/4
And lastly, another green marble
That would make 6 green marbles left and a total of just 19 left. So the probability at this point for green marbles = 6/19
Having and in probability means we multiply all
So this means the probability we are calculating is; 3/7 * 1/4 * 6/19 = 18/(28 * 19) = 9/(14 * 19) = 9/266
