If two lines are perpendicular, then:
[tex]m1\times m2=-1[/tex]From the equation:
[tex]y=-\frac{1}{3}x-5[/tex]We can conclude:
[tex]m1=-\frac{1}{3}[/tex]So:
[tex]\begin{gathered} -\frac{1}{3}\times m2=-1 \\ m2=3 \end{gathered}[/tex]Let:
[tex](x1,y1)=(0,-3)[/tex]Using the point-slope equation:
[tex]\begin{gathered} y-y1=m2(x-x1) \\ y-(-3)=3(x-0) \\ y+3=3x \\ solve_{\text{ }}for_{\text{ }}y\colon \\ y=3x-3 \end{gathered}[/tex]