Algebra
posted by Anita on .
In an interview of 50 math majors,
12 liked calculus and geometry
18 liked calculus but not algebra
4 liked calculus, algebra and geometry
25 liked calculus
15 liked geometry
10 liked algebra but neither calculus nor geometry
2 liked geometry and algebra but not calculus.
Of those surveyed, how many liked calculus and algebra?

If you want the number that liked both calculus and algebra, there is only one category that fits that description.
I hope this helps.