Question 876427
{{{y=(2/3)x-3}}} has a slope of {{{2/3}}} .
{{{18x+12y=-3}}}<-->{{{12y=-18x-3}}}<-->{{{y=(-18x-3)/12}}}<-->{{{y=(-18/12)x-3/12}}}<-->{{{y=(-3/2)x-1/4}}} has a slope of {{{-3/2}}} .
The product of the slopes is
{{{(2/3)(-3/2)=-1}}} so the lines are perpendicular.