First we add up the counts of all students that have passed a test, disregarding the subjects and any overlap.
Total Pass=70+62+84+82=298
Now, if 37 students passed all 4 tests, that means each category must include these same 37 students. Since we have 4 categories:
Total 4-Pass=37∗4=148
Now we subtract the numbers. The difference is the number of students that have passed at least a single test, but did not pass all N tests
Remaining=298−148=150
Now to solve the problem, we must maximize the overlap by assuming these kids all passed exactly 3 tests. It doesn't matter which tests exactly, and the numbers technically dont need to be evenly distributed. So we can just take the average
Avg 3-Pass = 150/3=50
At this point the original numbers and categories dont even matter anymore as we've slimmed the numbers down to include 100% of the kids that have passed, but we've now distributed them across only 3 tests instead of 4. So we can add these 2 numbers together
Total max passed =37+50=87
So out of 100 students, a maximum of 87 have all passed identical tests (100% overlap). And we can easily subtract these 2 to assume that all of the remaining kids have all failed all tests.
Max failed students=100−87=13
Bunuel what do you think of this analysis? maybe you have a clearer approach or explanation