The standard form of a line:
[tex]Ax+By=C[/tex]
We have the equation of a line in the slope-point form:
[tex]y-3=\dfrac{1}{2}(x+6)[/tex] use distributive property
[tex]y-3=\dfrac{1}{2}x+3[/tex] add 3 to both sides
[tex]y=\dfrac{1}{2}x+6[/tex] multiply both sides by 2
[tex]2y=x+12[/tex] subtract x from both sides
[tex]-x+2y=12[/tex] change the signs
[tex]x-2y=-12[/tex]