Consider the following premises. forall z: U(z) <-> T(z). exists z: U_1(z) -> T(z). forall z: R_3(z) -> U_1(z). Can we infer exists z: R_3(z) -> U(z) from them?
 From forall z: R_3(z) -> U_1(z), exists z: U_1(z) -> T(z) we can infer exists z: R_3(z) -> T(z). From forall z: U(z) <-> T(z) we can infer forall z: T(z) -> U(z). Finally, from exists z: R_3(z) -> T(z), forall z: T(z) -> U(z) we can infer exists z: R_3(z) -> U(z). Therefore, the answer is yes.