Respuesta :

TSO
[tex]\frac{3900}{5} = 780\sf ~kilometer~per~hour[/tex]

Your average speed is 780 kilometer per hour.
AL2006

Your average speed is exactly 3900 km per 5 hours.

In more familiar units,

     (3900 km) / (5 hr) = (3900/5) (km/hr)  =  780 km/hr

good job