Consider the following premises. p <-> s_1. p_3 <-> p. ~p_3. Can we infer ~s_1 from them? If possible, name the inference rules being used at each step.
 From p_3 <-> p, ~p_3 we can infer ~p via biconditional elimination. Finally, from p <-> s_1, ~p we can infer ~s_1 via biconditional elimination. Therefore, the answer is yes.