\(\sqrt{200}=\sqrt{100}⋅\sqrt{2}=10\sqrt{2}\text{.}\)

\(-7\sqrt{700}=-7⋅\sqrt{100}⋅\sqrt{7}=-7⋅10⋅\sqrt{7}=-70\sqrt{7}\text{.}\)

\(\sqrt{\frac{81}{100}}={\sqrt{81} \over \sqrt{100}}=\frac{9}{10}\text{.}\)

\(\sqrt{\frac{24}{49}}={\sqrt{24} \over \sqrt{49}}={\sqrt{24} \over 7}=\frac{1}{7}\sqrt{24}=\frac{1}{7}⋅2⋅\sqrt{6}=\frac{2}{7}\sqrt{6}\text{.}\)