Explanation:
12 green + 8 purple = 20 total
12/20 = 3/5 is the probability of getting green
Since the first marble is put back, the second selection has the same probability of getting green. Each selection is independent. This occurs with any replacement situation.
Because we have independent events, the probability of getting two green in a row is (3/5)*(3/5) = 9/25
