The answer is 1/10.
There are in total 20 marbles in the bag:
3 green + 2 yellow + 6 blue + 9 red = 20 marbles
There are 2 yellow marbles of total 20 marbles. 2 of 20 can be expressed as:
2/20 = 1/10.
Therefore, the probability of picking a yellow marble from the bag is 1/10.
