Bag a contains 4 red and 3 blue tickets. bag b contains 3 red and 1 blue ticket. a bag is randomly selected by tossing a coin and one ticket is removed from it. using a tree diagram, determine the probability that the ticket chosen is blue.

It's difficult to draw a tree diagram with this software.

Try to do it yourself & you will find the followings:

If A is selected (P (A) = 1/2) we can get ether red (p (A & red) = 4/7

so P (A∩red) = 1/2 x 4/7 = 4/14

Also we can get P (blue) = 3/7 & P (A∩blue) = 1/2 x 3/7 = 3/14

Same reasoning for B & you will get P (B∩read) 1/2 x 3/4 = 3/8

Also we can get P (B∩blue) = 1/2 x 1/4 = 1/8

Probability of blues is either 3/14 or 1/8

P (blue) = 3/8 + 1/8 = 19/56 = 0.339