Consider the following premises. p_1 <-> s_3. p_1 <-> s. w <-> s_3. ~w. Can we infer ~s from them? If possible, name the inference rules being used at each step.
 From w <-> s_3, ~w we can infer ~s_3 via biconditional elimination. From p_1 <-> s_3, ~s_3 we can infer ~p_1 via biconditional elimination. Finally, from p_1 <-> s, ~p_1 we can infer ~s via biconditional elimination. Therefore, the answer is yes.