How can i explain if 3x+4y=11, y=-3/4x+12 have any solutions?

Solve by using substitution.

3x + 4y = 11
y = [-3/4(x) + 12] ...... (1)

3x + 4y = 11

Substitute (1) for y.
3x + 4[-3/4(x) + 12] = 11
3x + (-3x) + 48 = 11
3x - 3x = 11 - 48
0 = -37
(no solutions)

They are 2 parallel lines,draw them.

http://www.freshstation.org/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=252&g2_serialNumber=1

they are parall no solution