[tex]\it a)\ \ x+3=0 \Rightarrow x=-3\\ \\ b)\ \ -x+9=2 \Rightarrow 9-2=x \Rightarrow x=7\\ \\ \\ c)\ \ 3x+3=-3\Big|_{:3} \Rightarrow x+1=-1\Big|_{-1} \Rightarrow x=-2\\ \\ \\ d)\ \ -4x-4=12\Big|_{:4} \Rightarrow -x-1=3\Big|_{+1} \Rightarrow -x=4\Big|_{\cdot(-1)} \Rightarrow x=-4\\ \\ \\ e)\ \ 3x=-15\Big|_{:3} \Rightarrow x=-5\\ \\ \\ f)\ \ -6x=36\Big|_{:(-6)} \Rightarrow x=-6\\ \\ \\g)\ \ x:(-2)=5\Big|_{\cdot(-2)} \Rightarrow x=-10\\ \\ \\ h)\ \ x:9=-11\Big|_{\cdot9} \Rightarrow x=-99[/tex]