Consider the following premises. p_4 <-> p_9. ~s. p -> p_4. p_9 <-> s. Can we infer ~p from them? If possible, name the inference rules being used at each step.
 From p_9 <-> s, ~s we can infer ~p_9 via biconditional elimination. From p_4 <-> p_9, ~p_9 we can infer ~p_4 via biconditional elimination. Finally, from p -> p_4, ~p_4 we can infer ~p via modus tollens. Therefore, the answer is yes.