Answers for "“There does not exist a woman who has taken a flight on every airline inthe world.”"

“There does not exist a woman who has taken a flight on every airline inthe world.”

¬∃w∀a∃f (P(w,f ) ∧ Q(f,a)) ≡ ∀w¬∀a∃f (P(w, f ) ∧ Q(f, a))

                            ≡ ∀w∃a¬∃f (P(w, f ) ∧ Q(f, a))

                            ≡ ∀w∃a∀f¬(P (w, f ) ∧ Q(f, a))

                            ≡ ∀w∃a∀f (¬P(w, f )∨¬Q(f, a))