A poll was taken of 100 students at a commuter campus to find out how they got to campus. The results were as follows:

28 said they drove alone.
37 rode in a carpool.
27 rode public transportation.
8 used both carpools and public transportation.
8 used both a carpool and sometimes their own cars.
4 used buses as well as their own cars.
3 used all three methods.

How many used none of the above-mentioned means of transportation?

28+37+27-8-8-4+3 = 75

so, 100-75 = 25 used none of the 3 methods

To find out how many students used none of the mentioned means of transportation, we need to calculate the number of students using each transportation method separately and then subtract that from the total number of students.

Let's break down the given information:
- 28 students said they drove alone.
- 37 students rode in a carpool.
- 27 students rode public transportation.
- 8 used both carpools and public transportation.
- 8 used both a carpool and sometimes their own cars.
- 4 used buses as well as their own cars.
- 3 used all three methods.

We can start by summing up the students who used individual forms of transportation:
- Students who drove alone: 28
- Students who rode in a carpool: 37 - 8 - 8 = 21 (subtracting the students who used both carpools and sometimes their own cars)
- Students who rode public transportation: 27 - 8 - 4 = 15 (subtracting the students who used both carpools and public transportation and those who used buses as well as their own cars)

Now, let's calculate the total number of students who used any of the mentioned methods:
Total = Students who drove alone + Students who rode in a carpool + Students who rode public transportation - Students who used all three methods
Total = 28 + 21 + 15 - 3 = 61

Finally, to find out how many students used none of the mentioned means, we subtract the total number of students using any of the methods from the total number of students:
Students using none of the mentioned means = Total number of students - Total number of students using any of the methods
Students using none of the mentioned means = 100 - 61 = 39

Therefore, 39 students used none of the above-mentioned means of transportation.