Consider the following premises. u <-> q_3. q_3 or t. ~u. Can we infer ~t from them? If possible, name the inference rules being used at each step.
 From u <-> q_3, ~u we can infer ~q_3 via biconditional elimination. Finally, from q_3 or t, ~q_3 we can infer t via disjunctive syllogism, which contradicts ~t. Therefore, the answer is no.