Consider the following premises. s -> q_9. s or ~q_9. q_9 -> s. Can we infer q_9 <-> s from them?
 From s or ~q_9 we can infer q_9 -> s. From s -> q_9, q_9 -> s we can infer s <-> q_9. From s <-> q_9 we can infer s -> q_9. Finally, from q_9 -> s, s -> q_9 we can infer q_9 <-> s. Therefore, the answer is yes.