#### Answer

$\frac{7}{3\sqrt {35}}$

#### Work Step by Step

$\frac{\sqrt 7}{\sqrt {45}}\times\frac{\sqrt 7}{\sqrt 7}$
=$\frac{\sqrt 7\times\sqrt 7}{\sqrt {45}\times\sqrt 7}$
=$\frac{7}{\sqrt {45\times7}}$
=$\frac{7}{\sqrt {315}}$
=$\frac{7}{\sqrt {9\times35}}$
=$\frac{7}{3\sqrt {35}}$