Guests at a recent party ate a total of fifteen hamburgers. each guest who was neither a student nor a vegetarian ate exactly one hamburger. no hamburger was eaten by any guest who was a student, a vegetarian, or both. if half of the guests were vegetarians, how many guests attended the party?
(1) the vegetarians attended the party at a rate of 2 students to every 3 non-students, half the rate for non-vegetarians.
(2) 30% of the guests were vegetarian non-students.