Consider the following premises. q_11 -> u. u -> q_11. p_9 <-> u. Can we infer q_11 -> p_9 from them?
 From u -> q_11, q_11 -> u we can infer u <-> q_11. From p_9 <-> u we can infer u -> p_9. From u <-> q_11 we can infer q_11 -> u. Finally, from q_11 -> u, u -> p_9 we can infer q_11 -> p_9. Therefore, the answer is yes.