Hum....I didn't see much of the responses. Anyhow here is my take -
consider the following matrix format - where S(Student), ~S (Non Student) V (Vegetarian) and ~V(Non Vegetarian). It is given that exctly 15 people had hamburger and no body else ate the hamburger(Student, Vegetarian or either of them). Also given that Vegetarian : Non Vegetrian = 1:1. Based on this, the matrix can be filled as follows - where a,b,c and x are unknowns. Need to find 2x = ? (The picture dipicted might not be as readable as I expected.
| S ~S Total
V | a b x
~V | c 15 x
| 2x - ???
From Clue 2, it is given that b= 30 % or 2x ==> From this we cannot find the exact value of x So options B and D are ruled out.
From clue 1, it is given that Vegetarian Students : Vegetarian non-students = 1 /2 (NonVegetarian students : NonVegetrain Non Students) Also Vegetarian students : Vegetarian non-students = 2: 3
==> 2/3 = (1/2)*(C/15) ==> 2/3 = c/30
==> c = 20 ==> x = 35
So total no of guests = 2x = 70.
My take is A(which is also OA)
Initially I was confused with the wording of clue 1. Could not represent it as a mathematical notation.