Answer
$k=180$, $y=\frac{180}{x}$
Work Step by Step
If y varies inversely as x, we know that the variables x and y can be related by the function $y=\frac{k}{x}$, where k is the constant of proportionality.
If $y=20$ when $x=9$, then we know that $20=\frac{k}{9}$. Multiply both sides by 9.
$k=20\times9=180$
Therefore, the constant of variation is $k=180$ and the inverse variation equation is $y=\frac{180}{x}$.
