I can help you but what is the operation of math
        
             
        
        
        
Answer and explain:
1st person: 70 % throws
70/100x80 = 56 out of 80 throws
2nd person: 60% throws
60/100x80 = 48 out of 80 throws
3rd person 50% throws
50/100x80 = 40 out of 80 throws
56+48+40/80x3 = 77/120
One equation that gives the estimated number of free throws (all the 3 people) is 77 out of 120. The best player will make about 56 out of 80 free throws. 
 
        
                    
             
        
        
        
The correct equation should look something like this:
y= -1x - 2
Consider the equation for a line:
y = mx + b,
Where ‘m’ is the slope
Where ‘b’ is the y-intercept.
From there you can plug in your known values for ‘m’ and ‘b’, and get the equation above. If you are still not convinced, I suggest you graph the function and observe its slope and y-intercept.
Hope this helps!
        
             
        
        
        
What is the full question? This is just a statement.