Question 275889
 7x+2y=10
-7x+y=-16
   3y=-6
 3y/3=-6/3
    y=-2

 7x+2y=10
-7x+y=-16 multiply second equation by -2 to eliminate y 

 7x+2y=10
14x-2y=-20
   21x=-10
21x/21=-10/21
    x=-10/21