Consider the following premises. forall x_13: P_13(x_13) <-> Q_13(x_13). P_13(c) or t. Q_13(c) or ~t. Can we infer Q_13(c) from them?
 From forall x_13: P_13(x_13) <-> Q_13(x_13) we can infer forall x_13: P_13(x_13) -> Q_13(x_13). From forall x_13: P_13(x_13) -> Q_13(x_13) we can infer P_13(c) -> Q_13(c). From Q_13(c) or ~t we can infer t -> Q_13(c). Finally, from P_13(c) -> Q_13(c), t -> Q_13(c), P_13(c) or t we can infer Q_13(c). Therefore, the answer is yes.