Translate the following inference to logic notation: For all x, x_7 is a sailor or x_7 is not an artist. There is at least one x for which x_7 is a sailor if and only if x_7 will take a plane. For all x, x_7 is an artist or x_7 will take a plane. Therefore there is at least one x for which x_7 is a sailor.
forall x: P(x) or ~Q(x). exists x: P(x) <-> R(x). forall x: Q(x) or R(x). Therefore exists x: P(x).