Question 1066482
.
We graph first line first and the second line second.


Two parallel lines in your case.


{{{graph( 330, 330, -10.5, 10.5, -10.5, 10.5,
          y = -3x+9, -3x+3
)}}}


Plots y = -3x + 9 (red) and y= -3x + 3 (green)