Question 153649
Two of your points are correct.
(x,-9) is incorrect.
{{{-3x+5(-9)=-15}}}
{{{-3x-45=-15}}}
{{{-3x=30}}}
{{{x=-10}}}
(-10,-9) 
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Plot the points on a graph and connect the points.
For a line, you only need two points.
We'll use your first two points:(0,-3) and (5,0) 
{{{drawing( 300, 300, -10, 6, -10, 6,grid( 1 ),blue(circle(0,-3,0.35)),blue(circle( 5, 0, .35)),blue(circle(-10,-9,.35)),green(line(-10,-9,20,9,0)))}}}
Then draw the line connecting the points.
As you can see (-10,-9) is also on the line.