The rise is the vertical distance between the two points, which is the difference between their y-coordinates. That makes the rise y2 − y1. The run between these two points is the difference in the x-coordinates, or x2 − x1.
        
             
        
        
        
A ↔ B ↔ C ↔ D ↔ E ↔ F
  
      8      7      
   ???
AB + BC + CD = AD   <em>segment addition postulate</em>
   +   8   +   7   = AD
   +       15        = AD
 AD         + 60    = 4AD
                   60    = 3AD
                   20    = AD
AB =  
    =  
    = 5
DE =  
   =  
    = 4
CD + DE + EF = CF   <em>segment addition postulate</em>
 7   +   4   + EF  = CF
      11        + EF  = CF
Answer: 11 + EF
Note: You did not provide any info about EF.  If you have additional information that you did not type in, calculate EF and add it to 11 to find the length of CF.
 
        
                    
             
        
        
        
1. The correct statement is the first one, which is: <span>Add the two equations, solve for y, and then substitute –1 for y to find x.
</span>
 2. Therefore, you have the following system of equations:
<span>
 4x+8y=20
 -4x+2y= -30
 3. When you a</span>dd the two equations, and clear the variable "y", you obtain:
 10y=-10
 y=-1
 4. Now, you must substitute -1 for y (y=-1) to find x, as below:
 4x+8y=20
 4x+8(-1)=20
 4x-8=20
 4x=20+8
 4x=28
 x=28/4
 x=7