Answer: B
Step-by-step explanation:
 
        
                    
             
        
        
        
Take the second equation and flip it around so the y on the left ends up on the right and the 4x on the right ends up on the left.  This makes all negatives positive and all positives negative.   -4x   + 12  = y 
Then add the first equation to the second equation 
4x   +12   = -7y
<u>-4x   + 12  </u>=<u> y </u>   this eliminates the x's
          <u>24</u> = -<u> 6y</u>            then divide by - 6
           - 6     - 6
         - 4    = y<u>
</u>So if you know that y = negative 4, you can substitute into either equation.  I pick the second one because I am a lazy person.  
  -y  + 12  = 4 x
-(-4) + 12 = 4 x     combine your numbers<u>
</u>   <u>  16     </u> = <u>4 x  </u>      then divide by 4<u>
</u>       4      =  x
So your solution is: x = 4 and y = -4 or this is also written (4, -4)
Does that work for you?
        
                    
             
        
        
        
A to line b
b to line c
c to line d
d to line e 
e to line a
        
             
        
        
        
40/3 or 13.333333- your welcome