Consider the following premises. w or q_7. q_2 <-> q_7. ~u_2. ~w or u_1. q_2 <-> u_2. Can we infer u_1 from them?
 From q_2 <-> u_2, ~u_2 we can infer ~q_2. From w or q_7, ~w or u_1 we can infer q_7 or u_1. From q_2 <-> q_7, ~q_2 we can infer ~q_7. Finally, from q_7 or u_1, ~q_7 we can infer u_1. Therefore, the answer is yes.