Answer
$216\ h$
Work Step by Step
Create a proportion using ratios as follows:
$$
\frac{6}{144 }=\frac{9}{x}
.$$
Set the product of the means equal to the product of the extremes and solve for $x$
$$
6 x=9\cdot 144\Longrightarrow x=\frac{9\cdot 144}{6}=216\ h
.$$
