Consider the following premises. P_12(g_1). forall x_12: ~Q_12(x_12). forall x_12: P_12(x_12) <-> Q_12(x_12). Can we infer t_3 from them?
 From forall x_12: P_12(x_12) <-> Q_12(x_12), forall x_12: ~Q_12(x_12) we can infer forall x_12: ~P_12(x_12). From forall x_12: ~P_12(x_12) we can infer ~P_12(g_1). From P_12(g_1) we can infer P_12(g_1) or t_3. Finally, from P_12(g_1) or t_3, ~P_12(g_1) we can infer t_3. Therefore, the answer is yes. Notice, however, that the premises were contradictory, so we can infer anything from them.