Consider the following premises. s -> t_3. u -> s. t_3 -> ~t_2. t_2. Can we infer ~u from them? If possible, name the inference rules being used at each step.
 From t_3 -> ~t_2, t_2 we can infer ~t_3 via modus tollens. From u -> s, s -> t_3 we can infer u -> t_3 via transitivity. Finally, from u -> t_3, ~t_3 we can infer ~u via modus tollens. Therefore, the answer is yes.