Consider the following premises. q_2 or ~u_3. t -> ~u. u. q_2 -> u_3. u_3 -> t. Can we infer q_2 from them?
 From q_2 or ~u_3 we can infer u_3 -> q_2. From t -> ~u, u we can infer ~t. From q_2 -> u_3, u_3 -> q_2 we can infer q_2 <-> u_3. From u_3 -> t, ~t we can infer ~u_3. Finally, from q_2 <-> u_3, ~u_3 we can infer ~q_2, which contradicts q_2. Therefore, the answer is no.