Answer
$P=\dfrac{k}{T}$
where k = constant of proportionality
Work Step by Step
RECALL:
(i)
If the quantities (or variables) $x$ and $y$ are related by the equation $y=kx$, then $y$ is directly proportional to $x$, where $k$ is the constant of proportionality.
(ii)
If the quantities (or variables) $x$ and $y$ are related by the equation $y=\dfrac{k}{x}$, then $y$ is inversely proportional to $x$, where $k$ is the constant of proportionality.
$P$ is given to be vary inversely (or inversely proportional) as $T$ therefore the equation that expresses the given statement is:
$P = \dfrac{k}{T}$ where k = constant of proportionality