Consider the following premises. forall x_12: R_12(x_12) <-> S_12(x_12). ~p_2. u_4 -> p_2. S_12(a_12) <-> u_4. Can we infer ~R_12(a_12) from them?
 From forall x_12: R_12(x_12) <-> S_12(x_12) we can infer R_12(a_12) <-> S_12(a_12). From u_4 -> p_2, ~p_2 we can infer ~u_4. From S_12(a_12) <-> u_4, ~u_4 we can infer ~S_12(a_12). Finally, from R_12(a_12) <-> S_12(a_12), ~S_12(a_12) we can infer ~R_12(a_12). Therefore, the answer is yes.