I can't figure this out. A poll was taken of 100 students at a commuter campus to find out how they got there
25 said they drove alone
26 rode in a carpool
32 rode in public transportation
8 used both carpools and public transportation
4used carpools and sometimes their own cars
6 used buses as well as their own cars 3 used all three methods
How many used none of the above mentioned means of transportation

Question

I can't figure this out. A poll was taken of 100 students at a commuter campus to find out how they got there 
25 said they drove alone
26 rode in a carpool
32 rode in public transportation 
8 used both carpools and public transportation
4used carpools and sometimes their own cars 
6 used buses as well as their own cars 3 used all three methods 
How many used none of the above mentioned means of transportation