Consider the following premises. p_7 or ~t. t or ~p_7. Can we infer ~(p_7 <-> t) from them?
 From p_7 or ~t we can infer t -> p_7. From t or ~p_7 we can infer p_7 -> t. Finally, from p_7 -> t, t -> p_7 we can infer p_7 <-> t, which contradicts ~(p_7 <-> t). Therefore, the answer is no.