Consider the following premises. u_3 -> q_6. q_6 -> u_3. p <-> q_6. ~p. Can we infer ~u_3 from them?
 From u_3 -> q_6, q_6 -> u_3 we can infer u_3 <-> q_6. From p <-> q_6, ~p we can infer ~q_6. Finally, from u_3 <-> q_6, ~q_6 we can infer ~u_3. Therefore, the answer is yes.