Question 168373
x+y=-4
y=-x-4 (red line)   
3x-y=-4
-y=-3x-4
y=3x+4 (green line) 
{{{ graph( 300, 200, -6, 5, -10, 10, -x -4, 3x +4) }}} (graph 300x200 pixels, x from -6 to 5, y from -10 to 10, of TWO functions -x -4 and 3x +4).
Solution (-2,-2)