Question 805820
{{{x-2y=6}}} is a linear equation.
Linear equations are equations of the form {{{Ax+By=C}}} ,
where A, B and C are numbers,
and A and B cannot be both zero at the same time.
In the case of {{{x-2y=6}}} you have {{{A=1}}}, {{{B=-2}}} and {{{C=6}}} .
Linear equations  are called linear equations for a good reason.
Their graphs are straight lines.
Since 2 points determine a line, all you would need to do is find two (x,y) pairs that satisfy the equation, plot them, and connect the dots with a straight line.
For {{{x-2y=6}}} , I would do it this way:
For {{{x=0}}} we get
{{{0-2y=6}}} --> {{{-2y=6}}} --> {{{y=6/(-2)}}} --> {{{highlight(y=-3)}}}
That means that the point {{{highlight((matrix(1,3,0,",",-3)))}}} is a point in the line.
For {{{y=0}}} we get
{{{x-2*0=6}}} --> {{{x-0=6}}} --> {{{highlight(x=6)}}}
That means that the point {{{highlight((matrix(1,3,6,",",0)))}}} is a point in the line.
So I plot the points, and connect them with a straight line:
{{{drawing(300,300,-2,8,-6,4,
grid(1),
blue(circle(0,-3,0.2)),blue(circle(6,0,0.2)),
blue(line(-2,-4,8,1))
)}}}

NOTES:
I marked the points with circles around them. That may not be the style your teacher wants.
Your teacher may want the work done and shown a certain way, such as calculating more points, displaying the (x,y) value pairs in the form of a table, or putting arrows and/or x/y labels on both ends of the x- and y-axes.