[tex]formula\ for\ average\ speed:\\
speed=\frac{distance}{time}\\\\ \frac{3\frac{2}{5}}{\frac{7}{8}}\frac{miles}{hours}=\frac{17}{5}*\frac{8}{7}=\frac{17*8}{5*7}=\\\\
\frac{136}{35}=27,2\frac{miles}{hour}\\\\
\boxed{Solution\ is\ v=27,2\frac{miles}{hour}}[/tex]
