Question

What is the solution to the system of linear equations y-x=4 and y+2x=1?

Answer 1

 -x + y = 4
2x + y = 1
     -3x = 3
      -3    -3
        x = -1
2x + y = 1
2(-1) + y = 1
     -2 + y = 1
   + 2       + 2
         y = 3
  (x, y) = (-1,3)