Hey Vishwa137.

Are you aware of probabilities and how they relate to Venn Diagrams?

In probability we can calculate P(A OR B) = P(A) + P(B) - P(A and B) and using this we get any statement of intersections and unions if we have enough information.

If you haven't come across this I can explain what it means but the idea is that you find the probabilities and then multiply it by the frequency to get the total number of people.