Question 293083
3u+v=16 
v=-3u+16 (red line)
3u=v+20
v=-3u+20 (green line)
{{{ graph( 300, 200, -6, 15, -10, 24, -3x +16, -3x +20) }}} (graph 300x200 pixels, x from -6 to 15, y from -10 to 24, of TWO functions -3x +16 and -3x +20). 
These lines are parallel.