Question 18
An, Binh and Chau make two statements each about Dung\'s age. An: “He is not $10$. He is $11$.” Binh: “He is not $11$. He is not $9$.” Chau: “He is not $12$. He is $10$.” One friend has both statements true, one has exactly one true, and one has both false. How old is Dung?
