Consider the following premises. t_1 <-> q_8. ~q_8. t_1 <-> s_1. Can we infer s_1 from them? If possible, name the inference rules being used at each step.
 From t_1 <-> q_8 we can infer t_1 -> q_8 via biconditional elimination. From t_1 -> q_8, ~q_8 we can infer ~t_1 via modus tollens. Finally, from t_1 <-> s_1, ~t_1 we can infer ~s_1 via biconditional elimination, which contradicts s_1. Therefore, the answer is no.