Consider the following premises. s_2 <-> q_9. s_2 <-> t. Can we infer q_9 -> t from them? If possible, name the inference rules being used at each step.
 From s_2 <-> q_9 we can infer q_9 -> s_2 via biconditional elimination. From s_2 <-> t we can infer s_2 -> t via biconditional elimination. Finally, from q_9 -> s_2, s_2 -> t we can infer q_9 -> t via transitivity. Therefore, the answer is yes.