Factor $20=2^{2}\times 5$. Rewrite the square root of the product $\sqrt{2^{2}\times 5}$ as the product of square roots $\sqrt{2^{2}}\sqrt{5}$. Take the square root of $2^{2}$.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $5$ and $6$ is $30$. Multiply $\frac{3\sqrt{5}}{5}$ times $\frac{6}{6}$. Multiply $\frac{\sqrt{6}}{6}$ times $\frac{5}{5}$.
To add or subtract expressions, expand them to make their denominators the same. Least common multiple of $30$ and $10$ is $30$. Multiply $\frac{\sqrt{5}}{10}$ times $\frac{3}{3}$.
