divide 3 root of 145 by 3 root 15.

$$\begin{gathered} \frac{3\sqrt{145}}{3\sqrt{15}} \\ =\frac{\sqrt{145}}{\sqrt{15}} \\ =\sqrt{\frac{145}{15}} \\ =\sqrt{\frac{29}{3}} \\ =\frac{\sqrt{29}}{\sqrt{3}} \\ =\frac{\sqrt{29}}{\sqrt{3}}\times \frac{\sqrt{3}}{\sqrt{3}} \\ =\frac{\sqrt{87}}{3} \end{gathered}$$