7. Use propositional logic to prove that the argument is valid (Y Z) (X Y) [Y (X W)] (Y Z) (Y W)

8. Use propositional logic to prove that the argument is valid (A B) B (A C) C

9. What inference rule is illustrated by the argument given? If Martina is the author, then the book is fiction. But the book is nonfiction. Therefore Martina is not the author.

M: Martina is the author

B: the book is fiction