
The picture places three groups, College Students, Singers and Dancers, as overlapping rectangles, and each of the seven inner boxes stands for a different combination of these three groups. The question asks for college students who dance but do not sing, so we can check each option in turn instead of deriving the region from scratch.
Only region R satisfies being a college student, being a dancer, and not being a singer, all at the same time.
Let's summarize:
So college students who are dancers but not singers are represented by R.
In the following figure, the smaller triangle represents teachers; the big triangle represents politicians; circle represents graduates and rectangle represents members of Parliament. Different regions are being represented by letters of English alphabet. On the basis of the above diagram, answer the following questions: 
Consider the Diagram. 500 Candidates appeared in an Examination comprising test in English, Hindi and Maths. The Diagram gives number of students who failed in different tests. What is the percentage of student who failed at least two subjects?
