Consider the following premises. p_9 <-> p_2. p_9 <-> p. ~p. Can we infer p_2 from them?
 From p_9 <-> p, ~p we can infer ~p_9. From p_9 <-> p_2 we can infer p_2 -> p_9. Finally, from p_2 -> p_9, ~p_9 we can infer ~p_2, which contradicts p_2. Therefore, the answer is no.