Answer:
The probability that all the marbles are red is 5 / 1012
Step-by-step explanation:
There are in total 5 + 10 + 9 = 24 marbles. Out of these 24 marbles, 5 are red.
Now if we randomly pick the first marble, the probability that it will be red is

For the second marble I pick, there are now 23 marbles in the bag. Out of these 23 marbles, 4 are red ( because I already took the 5th marble out). Therefore, the probability that the second marble will be red is

Similarly, for the third marble, the probability that it will be red will be

since there are 3 red marbles out of 22 total.
Therefore, the probability that ALL three marbles together will be red is


Hence, the probability that all the marbles are red is 5 / 1012.