75 +10n = 15n
75 = 5n
 15 = n
Therefore 15 classes
        
             
        
        
        
13x - 11y = -12
-13x -13x
___________
 -11y = -13x - 12
 ___ ______
 -11 -11
 -13x -12 
 y = _______
 -11
        
             
        
        
        
Answer:
-30
Step-by-step explanation:
To find slope, subtract two y's and then subtract the x's in the same order.
<u>12-(-18)</u>=<u>30</u>=-30
11-12       -1
You could also switch the order like this...
<u>-18-12</u>=<u>-30</u>=-30
12-11      1
As you can see, both of the ways of solving for slope resulted in -30.
Hope this helps!! Have a great day :3