No member of the Richardson Theater Group is both a performer and an administrator
Since Leon and Marta are both members of the Richardson Theater Group but neither is an administrator, it follows that both are performers
Not all of the employees of the Tedenco Company are salaried employees of that company. Since Mr. Lopez and Ms. Allen are both salaried employees of the Tedenco Company, it follows that they are not the only employees of the Tedenco Company.