Consider the following premises. p_3 <-> q_9. p_4 <-> q_9. Can we infer p_3 -> p_4 from them? If possible, name the inference rules being used at each step.
 From p_4 <-> q_9 we can infer q_9 -> p_4 via biconditional elimination. From p_3 <-> q_9 we can infer p_3 -> q_9 via biconditional elimination. Finally, from p_3 -> q_9, q_9 -> p_4 we can infer p_3 -> p_4 via transitivity. Therefore, the answer is yes.