Answer
$\sqrt{7}$
Work Step by Step
Using $\sqrt{\dfrac{x}{y}}=\dfrac{\sqrt{x}}{\sqrt{y}}$ or the quotient rule of radicals, the given expression, $
\dfrac{\sqrt{21}}{\sqrt{3}}
,$ simplifies to
\begin{array}{l}\require{cancel}
\sqrt{\dfrac{21}{3}}
\\\\=
\sqrt{7}
.\end{array}
Note that variables are assumed to have positive real numbers.
