Answer
$12.2$
Work Step by Step
Using $\frac{\sqrt{a}}{\sqrt{b}}=\sqrt{\frac{a}{b}}$, then the given expression is equivalent to
$$\begin{aligned}
\sqrt{12}\cdot\frac{5}{\sqrt{2}}&=\sqrt{\frac{12}{2}}\cdot5
\\&=
\sqrt{6}\cdot5
\\&=
5\sqrt{6}
\\&\approx
12.2
.\end{aligned}$$
Hence, rounded to the nearest tenth, the given expression is approximately $12.2$.