there are 60 minutes in one hour, thus, 45 miles per hour is 45 miles per 60 minutes, thus
[tex]\bf \begin{array}{ccll}
miles&minutes\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
45&60\\
240&m
\end{array}\implies \cfrac{45}{240}=\cfrac{60}{m}\implies m=\cfrac{240\cdot 60}{45}[/tex]
