Consider the following premises. ~q. r. u_2 <-> u. u_2 <-> q. Can we infer r and ~u from them? If possible, name the inference rules being used at each step.
 From u_2 <-> q, ~q we can infer ~u_2 via biconditional elimination. From u_2 <-> u, ~u_2 we can infer ~u via biconditional elimination. Finally, from r, ~u we can infer r and ~u via conjunction. Therefore, the answer is yes.