Answer
$\dfrac{3\sqrt{7}}{7}$
Work Step by Step
Multiplying both the numerator and the denominator by a factor that will make the denominator a perfect power of the radical, the rationalized-denominator form of the given expression, $
\dfrac{3}{\sqrt{7}}
,$ is
\begin{array}{l}\require{cancel}
\dfrac{3}{\sqrt{7}}\cdot\dfrac{\sqrt{7}}{\sqrt{7}}
\\\\=
\dfrac{3\sqrt{7}}{\sqrt{7(7)}}
\\\\=
\dfrac{3\sqrt{7}}{\sqrt{(7)^2}}
\\\\=
\dfrac{3\sqrt{7}}{7}
.\end{array}
