Example 1.1.8.
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:
| Subject: | A | B | C | AB | AC | BC | ABC |
| Failed: | 12 | 5 | 8 | 2 | 6 | 3 | 1 |
How many students failed at least one subject?