Consider the following premises. p_6 <-> t. w <-> t. p_6. Can we infer ~t from them?
 From w <-> t we can infer w -> t. From p_6 we can infer p_6 or w. From p_6 <-> t we can infer p_6 -> t. Finally, from p_6 -> t, w -> t, p_6 or w we can infer t, which contradicts ~t. Therefore, the answer is no.