Question:
When two quantities $\mathrm{x}$ and $\mathrm{y}$ are in---proportion or vary----they are written as $x \propto \frac{1}{y}$
Solution:
When two quantities $x$ and $y$ are in inverse proportion or vary inversely, they are written a $x \propto \frac{1}{y}$ [see definition of inverse
proportion]