Consider the following premises. forall x_10: T(x_10) or S_10(x_10). T(a_10) -> u_3. S_10(a_10) -> u_3. u_3 -> S_10(a_10). Can we infer u_3 from them?
 From forall x_10: T(x_10) or S_10(x_10) we can infer T(a_10) or S_10(a_10). From u_3 -> S_10(a_10), S_10(a_10) -> u_3 we can infer u_3 <-> S_10(a_10). From u_3 <-> S_10(a_10) we can infer S_10(a_10) -> u_3. Finally, from T(a_10) -> u_3, S_10(a_10) -> u_3, T(a_10) or S_10(a_10) we can infer u_3. Therefore, the answer is yes.