Consider the following premises. forall x_23: ~R_23(x_23). ~u_3. u <-> R_23(a_23). u_3 <-> q_7. Can we infer q_7 from them? If possible, name the inference rules being used at each step.
 From forall x_23: ~R_23(x_23) we can infer ~R_23(a_23) via universal instantiation. From u <-> R_23(a_23), ~R_23(a_23) we can infer ~u via biconditional elimination. Finally, from u_3 <-> q_7, ~u_3 we can infer ~q_7 via biconditional elimination, which contradicts q_7. Therefore, the answer is no.