You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.

[EX Q]: Question: In a class of 40 students, 10 did not opt for math. 15 did not opt for science and 2 did not opt for either. How many students of the class opted for both math and science?

 Option A: 13

 Option B: 15

 Option C: 7

 Option D: 17

 Option E: 18
[EX A]: Option C

[EX Q]: Question: The average age of 15 students of a class is 15 years. Out of these, the average age of 4 students is 14 years and that of the other 10 students is 16 years, The age of the 15th student is

 Option A: 11

 Option B: 12

 Option C: 9

 Option D: 14

 Option E: 15
[EX A]: Option C

[EX Q]: Question: What percent of 200 is 55?

 Option A: 0.25%

 Option B: 4%

 Option C: 25%

 Option D: 27.5%

 Option E: 250%
[EX A]:
Option D