x-9y=-43;3x+8y=68. Solution : {x,y} = {4,7}. System of Linear Equations entered : [1] 5x - 9y = -43 [2] 3x+ 8y = 68. Graphic Representation of the Equations : -9y + 5x = -43 8y + 3x = 68. Solve by Substitution : //Solve equation [2] for the variable y [2] 8y = -3x + 68 [2] y = -3x/8 + 17/2. // Plug this in for variable y in equation [1]