please find attached file as below:
i have try by using tree diagram until the part which i mark with BOX.other than that i have blur how to configure it..any advise
There are a total of 9 red discs and 7 black disks. The bags have been mixed thoroughly, so it is almost as if the contents have been dumped onto the ground and mixed. After mixing, there are 9 discs in the first bag. The probability of there being exactly three is:
The first three terms account for there being 3 red discs, and the last six terms account for there being 6 black discs.
We want the probability that Bag 1 ends up with its original contents.
There are two ways this can happen:
. .  A red is drawn from Bag 1 and a red is returned to Bag 1.
. .  A black is drawn from Bag 1 and a black is returned to Bag 1.
 A red is drawn from Bag 1: .
. . .Bag 2 now contains:7 red and 2 black discs:
. . .A red is drawn from Bag 2: .
. . . . .
 A black is drawn from Bag 1:
. . .Bag 2 now contains: 6 red and 3 black discs.
. . .A black is drawn from Bag 2: .
. . . . .