we know there are 5280 feet in 1 mile, and there are 3600 seconds in 1 hour.
[tex]\bf \cfrac{25 \underline{ft}}{sec}\cdot \cfrac{mi}{5280 \underline{ft}}\cdot \cfrac{3600 \underline{sec}}{hr}\implies \cfrac{25\cdot 3600}{5280}\cfrac{mi}{hr}\implies \cfrac{375}{22}\cfrac{mi}{hr}\implies 17.0\overline{45}\frac{mi}{hr}[/tex]