Question 281566
4x=y+5
y=4x-5 (red line)
8x-5=2y 
2y=8x-5
y=8x/2-5/2
y=4x-2.5 (green line)
{{{ graph( 300, 200, -6, 5, -10, 10, 4x -5, 4x -2.5) }}} (graph 300x200 pixels, x from -6 to 5, y from -10 to 10, of TWO functions 4x -5 and 4x -2.5). 
No unique solution for x & y because these are parallel lines.