Consider the following premises. q -> q_12. p <-> q. p or ~q_12. Can we infer p <-> q_12 from them? If possible, name the inference rules being used at each step.
 From p or ~q_12 we can infer q_12 -> p via rewriting. From p <-> q we can infer p -> q via biconditional elimination. From p -> q, q -> q_12 we can infer p -> q_12 via transitivity. Finally, from p -> q_12, q_12 -> p we can infer p <-> q_12 via biconditional introduction. Therefore, the answer is yes.