Consider the following premises. ~p_3 or q_3. u_3 or ~q_3. p_3 or r. u_3 <-> r. Can we infer ~u_3 from them?
 From p_3 or r, ~p_3 or q_3 we can infer r or q_3. From u_3 or ~q_3 we can infer q_3 -> u_3. From u_3 <-> r we can infer r -> u_3. Finally, from r -> u_3, q_3 -> u_3, r or q_3 we can infer u_3, which contradicts ~u_3. Therefore, the answer is no.