Consider the following premises. u or ~q_16. t_3 or q_16. t_3 -> p_20. p_20 -> t_3. ~p_20. Can we infer ~u from them?
 From p_20 -> t_3, t_3 -> p_20 we can infer p_20 <-> t_3. From u or ~q_16 we can infer q_16 -> u. From p_20 <-> t_3, ~p_20 we can infer ~t_3. From t_3 or q_16, ~t_3 we can infer q_16. Finally, from q_16 -> u, q_16 we can infer u, which contradicts ~u. Therefore, the answer is no.