\[S_{1} = 5 \cdot 62 = 310\ км.\]
\[S_{2} = 3 \cdot 52 = 156\ км.\]
\[S = 310 + 156 = 466\ км.\]
\[t = 5 + 3 = 8\ часов.\]
\[V_{ср.} = S\ :t = 466\ :8 =\]
\[= 58,25\frac{км}{ч} - средняя\ \]
\[скорость.\]
\[Ответ:58,25\ \frac{км}{ч}.\]