Hello! Put two letters at random, each letter has three mailboxes to choose from, and * * * has 3*3=9 choices. P{X=0, Y= 1} means that there is no letter in the first mailbox and there is letter in the second mailbox. There are two choices for this letter, so the probability is 2/9; P{X= 1, Y= 1} means that there is a letter in each of the first two mailboxes. There are two choices for the letter in the first mailbox (the other letter can only be in the second mailbox), so the probability is 2/9. The economic mathematics team will help you solve the problem, please adopt it in time. thank you