You can put this solution on YOUR website! 3u+v=6
3x+y=6
y=-3x+6 (red line)
3u=v+12
3x=y+12
y=3x-12 (green line) (graph 300x200 pixels, x from -6 to 5, y from -10 to 15, of TWO functions -3x +6 and 3x -12).
These 2 equations are independent (exactly 1 solution).