The symbol $y\propto x$ means $y$ is proportional to $x$. In GCSE questions, you usually replace $\propto$ with an equation using a constant $k$.

For direct proportion, $y=kx$, so both variables scale by the same factor. For inverse proportion, $y=\frac{k}{x}$, so when one variable gets bigger, the other gets smaller.

Watch the wording carefully. If $A$ is directly proportional to the square of $B$, write $A=k{B}^2$, but if $P$ is inversely proportional to the cube of $Q$, write $P=\frac{k}{Q^3}$.