Find out the probability of each event
so
Event 1: choosing a white marble from Bag A
total marbles Bag A=12
total white marbles Bag A=6
P=6/12
simplify
P=1/2 or P=0.50
Event 2: choosing a white marble from Bag B.
total marbles Bag B=20
total white marbles Bag B=9
P=9/20 or P=0.45
Event 3: choosing a red marble from Bag B
total marbles Bag B=20
total red marbles Bag B=0
P=0/20 -----> P=0
Event 4: choosing a white or green marble from Bag A
total marbles Bag A=12
total white or green marble from Bag A=12
P=12/12 --------> P=1
therefore
The answer is
Event 3, Event 1, Event 2, Event 4