Let A be the set of people who like coffee and B be the set of people who like tea. Given that n(A)=37,n(B)=52 and n(A⋃B)=70. Since, every person likes at least one drink (0 elements outside A and B), we have: n(A⋃B)=n(A)+n(B)−n(A⋂B) ⇒70=37+52−n(A⋂B) ⇒n(A⋂B)=89−70=19 People who like coffee and NOT tea is given by n (A−B)=n(A)−n(A⋂B)=37−19=18.