; Eq3 := y+z = -5; y := -5 -z: Eq2 := x + 3* z = 2; x := 2 - 3*z: Eq1 := w - 7*z = 8; w := 8 + 7*z: {[w,x,y,z]}; backsub(matrix(3,5,[1,0,0,-7,8, 0,1,0,3,2, 0,0,1,1,-5]));