Consider the following premises. p <-> q_15. ~q_15. p -> q_15. Can we infer ~p or t from them? If possible, name the inference rules being used at each step.
 From p <-> q_15 we can infer q_15 -> p via biconditional elimination. From q_15 -> p, p -> q_15 we can infer q_15 <-> p via biconditional introduction. From q_15 <-> p, ~q_15 we can infer ~p via biconditional elimination. Finally, from ~p we can infer ~p or t via addition. Therefore, the answer is yes.