,

$$\frac{40}{100}\times x=\frac{y}{100}\times 300$$

,

\begin{eqnarray*}
\frac{40}{100}x & = & \frac{y}{100}\times300\\
40x & = & 300y\\
\frac{x}{y} & = & \frac{300}{40}\\
& = & \frac{15}{2}
\end{eqnarray*}