notice the proportions below. Keep in mind that 1 hour is 60 minutes.
[tex]\bf \begin{array}{ccll}
miles&minutes\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
0.75&1\\
x&60
\end{array}\implies \cfrac{0.75}{x}=\cfrac{1}{60}\implies \cfrac{0.75\cdot 60}{1}=x\implies 45=x[/tex]