In a class of 94 students 41 are taking French, 22 are taking German. Of the students taking French or German, 9 are taking both courses. How many students are not enrolled in either course?  Choices
A) 6 B) 15 C) 24 D) 33 E) 40

Rationale: "formula for calculating two overlapping sets : a + b - both + not ( a or b ) = total so in our task we have equation : 41 ( french ) + 22 ( german ) - 9 ( both ) + not = 94 54 + not = 94 not = 94 - 54 = 40 so answer is e"
Answer: E