Consider the following premises. forall x_9: ~Q_7(x_9). exists x_9: P_9(x_9) <-> Q_7(x_9). forall x_9: P_9(x_9). Can we infer exists x_9: Q_9(x_9) from them?
 From forall x_9: P_9(x_9) we can infer forall x_9: P_9(x_9) or Q_9(x_9). From exists x_9: P_9(x_9) <-> Q_7(x_9), forall x_9: ~Q_7(x_9) we can infer exists x_9: ~P_9(x_9). Finally, from forall x_9: P_9(x_9) or Q_9(x_9), exists x_9: ~P_9(x_9) we can infer exists x_9: Q_9(x_9). Therefore, the answer is yes. Notice, however, that the premises were contradictory, so we can infer anything from them.