Translate the following inference to logic notation: For all x, if x_7 drives a car, then x_7 is playing tennis. There is at least one x for which if x_7 drives a car, then x_7 is playing tennis. For all x, if x_7 plays tennis, then x_7 is driving a car. Therefore there is at least one x for which x_7 will play tennis if and only if x_7 will drive a car.
forall x: P(x) -> Q(x). exists x: P(x) -> Q(x). forall x: Q(x) -> P(x). Therefore exists x: Q(x) <-> P(x).