Total envelopes: 3 + 1 + 3 + 2 = 9 with a total of 3 green ones.
Probability of picking green first: 3 out of 9 = 3/9 = 1/3
There are 8 envelopes left, with 2 green ones.
Probability of picking a green one is 2 out of 8 = 2/8 = 1/4
There are 7 envelopes left and 1 green one.
Probability of picking green is 1 out of 7 = 1/7
Probability of picking all 3 = 1/3 x 1/4 x 1/7 = 1/84
