Here is the problem.

70 students are enrolled in Math, English, or German. 40 students are in Math, 35 are in English, 30 are in German. 15 students are enrolled in all 3 of the courses. How many of the students are enrolled in exactly two of the courses: Math, English, and German?

The book has very bad explanation and possibly wrong answer for this problem. Using my own logic I get a different answer than the book.

Please let me know what you guys get as answer for this problem.

thank you.

P.S. Anyone preparing for GMAT, please PM me if you're good at math. We might be able to help eachother out! Thanks.