Consider the following premises. s_1 <-> s. q_7. s -> ~q_7. t_1 <-> s_1. Can we infer t_1 from them?
 From s -> ~q_7, q_7 we can infer ~s. From s_1 <-> s, ~s we can infer ~s_1. Finally, from t_1 <-> s_1, ~s_1 we can infer ~t_1, which contradicts t_1. Therefore, the answer is no.