Let U = set of students in a school.
A = set of students taking tea
B = set of students taking coffee
Then n(∪) = 600; n(A) = 150; n(B) = 225; n(A∩B) = 100
∴ n(Au B) = n(A) + n(B)-n(A∩B) = 150 + 225-100 =275
Now n(A’∩B’) = n(A∪B)
= n(∪)-n(A∪5) = 600-275 = 325
∴ 325 students were taking neither tea nor coffee.