Answer
$v=\dfrac{k}{z}$
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.
$v$ is given to be inversely proportional to $z$ therefore the equation that expresses the given statement is:
$v = \dfrac{k}{z}$ where k = constant of proportionality