Well all you need to do to write the linear equation for this function. I assume you want to know, is that you must obtain 2 points, and calculate the slope, then place the info within the following form. 
Y = mx + b 
1 of the points has to be the y intercept, which can be obtained from the graph, and the other, any other point, which can also be the X intercept. 
So, X intercept - (2,0)
Y intercept - (0,3). 
Slope = y/X = 3-0/0-2
Slope = 3/-2 or -3/2. 
Now put everything together in form: 
Y = mx + b 
Y = -3/2x + 3. 
I believe this is the solution.
        
                    
             
        
        
        
The total cost before books are printed is $1200 (the constant).
The change to the total cost is the x, which is a variable, and can change depending on the amount of books printed.
hope this helps
        
             
        
        
        
Answer:-2,-3
Step-by-step explanation:
 
        
                    
             
        
        
        
Answer:
constant of proportionality, k is 3
Step-by-step explanation:
constant, k= y/x
k=9/3
  = 3
 
        
             
        
        
        
The number is -11/4 less than -8/3