Answer
$p=2(l+h)$
Work Step by Step
$y$ varies directly with $x,$ or $y$ is directly proportional to $x$,
if there is a nonzero number $k$ such that$ y=kx.$
The number $k$ is called the constant of proportionality.
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Here, y is "the perimeter, p", and
x = "sum of l and h"
The given model is
$ p=k(l+h)\quad$
Given that $k=2,$ it means that
$p=2(l+h)$
