You can put this solution on YOUR website! L1 HAS A SLOPE OF: (6-0)/(0+4)=6/4=1.5 IS THE SLOPE OF THE LINE THROUGH THESE 2 POINTS.
THIS EQUATION IS:
Y=1.5X+6 (RED LINE)
Y=mX+b IS THE LINE EQUATION. WITH A SLOPE OF 1.5 & PASSING THROUGH THE ORIGIN (0,0) WE HAVE:
Y=1.5X (GREEN LINE)
(graph 300x200 pixels, x from -6 to 5, y from -10 to 10, of TWO functions y = 1.5x +6 and y = 1.5x).