Consider the following premises. r -> q_7. s_2 or ~q_7. s_2 -> r. Can we infer s_2 <-> q_7 from them?
 From s_2 or ~q_7 we can infer q_7 -> s_2. From s_2 -> r, r -> q_7 we can infer s_2 -> q_7. Finally, from s_2 -> q_7, q_7 -> s_2 we can infer s_2 <-> q_7. Therefore, the answer is yes.