Answer
$6x^{3}\sqrt x$
Work Step by Step
$\sqrt (36x^{7})=\sqrt (36\times x^{6}\times x)=\sqrt 36\times\sqrt (x^{6})\times\sqrt x=6x^{3}\sqrt x$
We know that $\sqrt 36=6$, because $6^{2}=36$.
We also know that $\sqrt (x^{6})=x^{3}$, because $(x^{3})^{2}=x^{3\times2}=x^{6}$
