In the following figure small square represents the persons who know English,…

Concept: In a Venn diagram built from more than two overlapping figures, every distinct region carries its own count, and each region represents the persons belonging to exactly the combination of categories it lies inside.

To find how many persons belong to two particular categories together, add the counts of every region that lies inside both of those two shapes, regardless of whether the region also lies inside any other shape.

Application: In the figure, the triangle is marked Marathi and the big square is marked Telugu by the arrows drawn next to them. Read off every region that lies inside the triangle, then keep only the ones that also lie inside the big square.

1. Regions inside the triangle in the figure: 4, 6, 3, 7 and 9.

2. Among these, only 6 and 7 are also enclosed by the big square's boundary; 4, 3 and 9 lie inside the triangle but outside the big square.

3. So the persons who know both Marathi and Telugu are counted by regions 6 and 7 only: 6 + 7 = 13.

Cross-check: If region 9 were also counted (6 + 7 + 9 = 22), that total is not among the given choices, while 13 is -- confirming that 6 and 7 are the correct regions to add, and that the saved answer, 13, is right.