Question 983599
Two ways:
draw a table of points.
y=0, x=0  (0,0) is one
choose something for x, like 1
x=1, y=-3  (1,-3) is another.
Two points determine a line.  Plot the points, draw the line.

Second way:
y-intercept is 0 y=-3x+0 is another way to write the line.
slope is -3, over 1 and down 3.
Draw the line

graph

{{{graph(300,200,-10,10,-10,10,-3x)}}}