Question 604392
{{{-x-3y=-9}}} is a linear equation.
For linear equations, the graph is a straight line.
To draw them you just need to determine 2 points, plot them, and connect them with a straight line.
I try to chose points that make the calculations easy and the graph "pretty".
If I am lucky, the point with x=0 and the point with y=0 will do.
Because I do not like to mess with so many minus signs, I will first multiply both sides of {{{-x-3y=-9}}} times {{{(-1)}}} to get the equivalent equation
{{{x+3y=9}}}
With x=0, we get {{{0+3y=9}}} --> {{{3y=9}}} --> {{{3y/3=9/3}}} --> {{{y=3}}}
That gives us the point (0,3)
With y=0, we get {{{x+3*0=9}}} --> {{{x+0=9}}} --> {{{x=9}}} for the point (9,0).
So we plot the points and connect them to get
{{{drawing(300,300,-3,12,-5,10,
grid(1), blue(circle(0,3,0.3)),
blue(circle(9,0,0.3)),blue(line(-3,4,12,-1))
)}}}