Answer :
[tex]64\ \frac{mile}{hour}=x\frac{feet}{second}\\\\
Converting\ unites:\\
1\ mile= 5280\ feet\\
1\ hour=\ 3600\ second\\\\
64\frac{mile}{hour}=64*\frac{5280feet}{3600second}=\frac{33792\ feet}{3600\ second}=93,9\frac{feet}{second}[/tex]