It's possible someone messed with the axle spacing but the tire sits too far to the left (NDS) correct? There doesn't seem to be much space on the DS. If that's the case and it's relatively true, it probably needs to be re-dished or the frame might be bent...or both. I'd check the frame with the string test previously described. If you take it to get it trued and dished, you might want to think of what you want to do with the bike. If that's a Shimano hyperglide cassette, you can swap out the hub body ($30-$50) and upgrade to 9-speed. If you plan to do that, wait, because you'll need to get the axle spaced properly and likely will need to get the wheel dished anyway. If you're going to leave it as is, take it in and get it re-dished.