Of course, this is not a mathematics question. There could be many acceptable answers.

Possible answer 1.

It sounds a bit like the riddle whose answer is that the story takes place at the North Pole: At a point where the latitude is a circle of length 1.5X miles, you can travel X miles west to your destination, then continue .5X miles west to return.

Possible answer 2.

There is a one-way street X miles long from A to B. In the other direction the road is half as long. (This is actually the case when traveling from my office to my locker in the Phys Ed building, except the appropriate units are meters and not miles: There is a door blocking the short route going toward my locker, so I must go the long way around. For the return trip, I can exit from that door and walk a much shorter distance.)