Consider the following premises. s <-> w. u_2 -> s. s -> p_8. p_8 -> u_2. ~w. Can we infer ~p_8 from them? If possible, name the inference rules being used at each step.
 From p_8 -> u_2, u_2 -> s we can infer p_8 -> s via transitivity. From s <-> w, ~w we can infer ~s via biconditional elimination. From s -> p_8, p_8 -> s we can infer s <-> p_8 via biconditional introduction. Finally, from s <-> p_8, ~s we can infer ~p_8 via biconditional elimination. Therefore, the answer is yes.