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?	Choose the most appropriate option:
A) 13	B) 15	C) 7	D) 17	E) 18
40 students total   10 did not opt for math   15 did not opt for science   2 did not opt for either   Total of 30 students in math and 13 did not opt for sci but did for math   30-13=7   7 students of the class opted for both math and science   Answer:   C. 7
<result>C</result>
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?