Consider the following premises. p <-> t. p or ~s. ~t. s or ~p. Can we infer ~s from them? If possible, name the inference rules being used at each step.
 From p <-> t, ~t we can infer ~p via biconditional elimination. From s or ~p we can infer p -> s via rewriting. From p or ~s we can infer s -> p via rewriting. From s -> p, p -> s we can infer s <-> p via biconditional introduction. Finally, from s <-> p, ~p we can infer ~s via biconditional elimination. Therefore, the answer is yes.