Consider the following premises. forall x_7: R_7(x_7) <-> S_7(x_7). S_7(b). Can we infer R_7(b) from them?
 From forall x_7: R_7(x_7) <-> S_7(x_7) we can infer R_7(b) <-> S_7(b). From R_7(b) <-> S_7(b) we can infer S_7(b) -> R_7(b). Finally, from S_7(b) -> R_7(b), S_7(b) we can infer R_7(b). Therefore, the answer is yes.