Consider the following premises. ~r. r <-> q_6. r -> q_6. Can we infer ~q_6 from them?
 From r <-> q_6 we can infer q_6 -> r. From r -> q_6, q_6 -> r we can infer r <-> q_6. Finally, from r <-> q_6, ~r we can infer ~q_6. Therefore, the answer is yes.