Consider the following premises. ~R_21(a_21). t <-> w_1. w_1 <-> S_21(a_21). forall x_21: R_21(x_21) <-> S_21(x_21). Can we infer t <-> w_1 from them? If possible, name the inference rules being used at each step.
That is one of the premises. Therefore, the answer is yes.