Consider the following premises. t <-> q_8. r_3. r_3 -> t. Can we infer ~q_8 from them?
 From t <-> q_8 we can infer t -> q_8. From r_3 -> t, t -> q_8 we can infer r_3 -> q_8. Finally, from r_3 -> q_8, r_3 we can infer q_8, which contradicts ~q_8. Therefore, the answer is no.