If you use metric conversion (shown below), you will find that 9 meters = 90 cm. Tell me if you need further explanation.
        
             
        
        
        
Assume N students
Student 1 can get (n-1) papers
Student 2 can get (n-1) papers
Student 3 can get (n-1) papers
etc
Student N can get (n-1) papers
So for N students you can have N(n-1)
        
             
        
        
        
117 - 30 = 87
87/3 = 29
The car was towed 29 miles
hope this helps