Question 706134
We're going to apply the "elimination" method:
y=x+8    
-x+3y=10
.
Move all the x's and y's to the left:
-x+ y= 8    
-x+3y=10
.
Multiply both sides of the TOP equation by -1.  Then combine BOTH equations together to eliminate the x term:
 x- y=-8    
-x+3y=10
-----------
   2y=2
    y = 1
.
Now, we substitute y=1 into:
y=x+8    
1=x+8    
-7=x
.
solution: (x,y) = (-7,1)