Consider the following premises. p -> u. p_11 -> p. t <-> p_11. ~u. Can we infer ~t from them?
 From p_11 -> p, p -> u we can infer p_11 -> u. From t <-> p_11 we can infer t -> p_11. From t -> p_11, p_11 -> u we can infer t -> u. Finally, from t -> u, ~u we can infer ~t. Therefore, the answer is yes.