Let A and B be the sets of those playing hockey and cricket, respectively.
Then n(A)=28, n(B)=33 and n(A∪B)=60−14=46.
Number of pupils who play both =n(A∩B)=n(A)+n(B)−n(A∪B)=28+33−46=15
Note: The formulae used above can be extended for more than two sets also.
For any three sets A, B, and C,
n(A∪B∪C)=n(A)+n(B)+n(C)−n(A∩C)−n(B∩C)−n(A∩C)+n(A∩B∩C)