Answer:
I would assume they drove a car.
If so, then Dallas to Houston: 239.3 miles.
Then, Houston to Austin: 165.3 miles
Shortest route back to Texas: 913.5.
I used g o o g l e m a p s to find my answer.
Now add the numbers up:
239.3+165.3+913.5= 1318.1
They traveled 1318.1 miles in all.