#### Answer

$10x$

#### Work Step by Step

RECALL:
For any non-negative real numbers a and b,
$\sqrt[n]{a} \cdot \sqrt[n]{b} = \sqrt[n]{ab}$
Use the rule above to obtain:
$=\sqrt{(20x)(5x)}
\\=\sqrt{100x^2}$
Factor the radicand (expression inside the radical sign) so that at least one factor is a perfect square, and then simplify to obtain:
$=\sqrt{(10x)(10x)}
\\=\sqrt{(10x)^2}
\\=10x$
(There is no need for the absolute value since $x$ is a positive, real number.)