Consider the following premises. t_1 <-> q_8. t_1 <-> s. Can we infer s -> q_8 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 <-> s we can infer s -> t_1 via biconditional elimination. Finally, from s -> t_1, t_1 -> q_8 we can infer s -> q_8 via transitivity. Therefore, the answer is yes.