Answer:
The automobile would take 6.5 hours to complete the trip.
Step-by-step explanation:
This is a case of a inverse variation relationship because when you increase the speed of traveling the time of arriving will reduce, now we have to define the equation and the variables:
Inverse variation equation: 
: speed of the bus, 65 miles per hour
: time to Austin by bus, 8 hours
: speed of the automobile, 80 miles per hour
: time to Austin by automobile, unknown
Now we can replace the values in the equation and clear
, this is:

The automobile would take 6.5 hours to complete the trip.