Two identical contaniers contain marbles. Container 1 has 2 white marbles and one red marble. Container 2 has one white marble and one red marble. Suppose you select a container at random and then draw out a marlbe. What is the probability of drawing a white marble?

For answering my question I used a tree diagram, and for my answer I got 3 out of 5. Is this right?

I see you posted this twice. Here's how you do these types of problems.

Forget the tree diagram. Do it this way.

P(\text{white ball})=P(\text{container 1}) \times P(\text{white from container 1})\\ + P(\text{container 2}) \times P(\text{white from container 2})=(1/2)(2/3)+(1/2)(1/2)=\fbox{7/12}

Maybe now since I showed you, you can tackle other similar problems. Okey-doke?