Let f(x)=(3x+6)/(2x-12)=(3(x+2))/(2(x-6))
Let's build the sign chart
color(white)(aaaa)xcolor(white)(aaaa)-oocolor(white)(aaaaaa)-2color(white)(aaaaaaa)6color(white)(aaaaaa)+oo
color(white)(aaaa)x+2color(white)(aaaaaa)-color(white)(aaa)0color(white)(aaa)+color(white)(aaaaaa)+
color(white)(aaaa)x-6color(white)(aaaaaa)-color(white)(aaa)0color(white)(aaa)-color(white)(aa)||color(white)(aaa)+
color(white)(aaaa)f(x)color(white)(aaaaaaa)+color(white)(aaa)0color(white)(aaa)-color(white)(aa)||color(white)(aaa)+
Therefore,
f(x)<=0 when x in [-2,6)
graph{(3x+6)/(2x-12) [-22.8, 22.83, -11.4, 11.4]}