Consider the following premises. p_7 <-> q. p_7 or ~q. Can we infer q <-> p_7 from them?
 From p_7 or ~q we can infer q -> p_7. From p_7 <-> q we can infer p_7 -> q. Finally, from q -> p_7, p_7 -> q we can infer q <-> p_7. Therefore, the answer is yes.