The correct option is B 150
Let, T be the set of people who preferred Tea and C be the set of people who preferred Coffee.
Given : n(T)=300,n(C)=100,n(T∩C)=50andn(U)=500
To find : No. of people who do not prefer any of drink =n(T∩C)′
We know,
n(T∪C)=n(T)+n(C)−n(T∩C)
So, n(T∪C)=300+100−50
=350
We also know,
n(T∪C)+n(T∪C)′=n(U)
n(T∪C)′=500−350
=150