okay so she has 6+8+5+9 marbles. that is 28
the chance that she will first pick a green marble is the number of green marbles over the total number of marbles or 8/28 this is reduced to 2/7
If she does not replace the marble the next pick there will be 27 total marbles.
the chance of a white marble is white marbles/all marbles
or 9/27 reduced to 1/3
the probability of both is the first probability times the second probability
2/7 times 1/3 or 2/21