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.

[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
[A]: Option C


[Q]: Question: P is three times as fast as Q and working together, they can complete a work in 18 days. In how many days can Q alone complete the work?

 Option A: 24

 Option B: 77

 Option C: 88

 Option D: 55

 Option E: 778
[A]: Option A


[Q]: Question: Of the 5 numbers, whose average is 75, the first is one-fourth of the sum of the last 4. The first number is?

 Option A: 75

 Option B: 80

 Option C: 78

 Option D: 56

 Option E: 67
[A]:
Option A