Consider the following premises. t <-> q_6. ~q_6. t -> q_6. Can we infer t from them?
 From t <-> q_6 we can infer q_6 -> t. From t -> q_6, q_6 -> t we can infer t <-> q_6. Finally, from t <-> q_6, ~q_6 we can infer ~t, which contradicts t. Therefore, the answer is no.