Consider the following premises. p_8 <-> t. ~t. ~p_8 -> p. Can we infer ~p from them? If possible, name the inference rules being used at each step.
 From p_8 <-> t, ~t we can infer ~p_8 via biconditional elimination. Finally, from ~p_8 -> p, ~p_8 we can infer p via modus ponens, which contradicts ~p. Therefore, the answer is no.