Consider the following premises. ~p. ~p_2 -> p_1. p_2 -> q_12. p <-> q_12. Can we infer p_1 from them? If possible, name the inference rules being used at each step.
 From p <-> q_12, ~p we can infer ~q_12 via biconditional elimination. From p_2 -> q_12, ~q_12 we can infer ~p_2 via modus tollens. Finally, from ~p_2 -> p_1, ~p_2 we can infer p_1 via modus ponens. Therefore, the answer is yes.