The number of feet between 2 objects varies directly as the number of miles. If the distance between 2 objects is 2 1/2 miles or 13,200 feet how many feet are equivalent to a distance of 7 miles
[tex]\bf \stackrel{feet}{f}=k\stackrel{miles}{m}\textit{ we also know that }
\begin{cases}
m=2\frac{1}{2}\\
f=13200
\end{cases}\implies 13200=k\cdot 2\frac{1}{2}
\\\\\\
13200=k\cfrac{5}{2}\implies \cfrac{13200\cdot 2}{5}=k\implies 5280=k
\\\\\\
\boxed{f=5280m}
\\\\\\
\textit{when m = 7, what is \underline{f}?}\qquad \qquad f=5208(7)[/tex]