# Failed exams

From Math Puzzle Wiki

Here is a typical set theory problem

## Puzzle

An examination in three subjects, Algebra, Biology, and Chemistry, was taken by 41 students. The following table shows how many students failed in each single subject and in their various combinations.

Subjects: | A | B | C | AB | AC | BC | ABC |
---|---|---|---|---|---|---|---|

Failed: | 12 | 5 | 8 | 2 | 6 | 3 | 1 |

How many students passed all three subjects?

## Help

**Hint**

The answer is not 4.