013 LXX vs MT

The Old Testament (OT) books in most of our Bible are translated roughly following the Hebrew text of the Masoretic Text (MT) but the differences between the Septuagint (LXX) and the (MT) can't be explained by translation differences. Some Dead Sea Scrolls (DSS) support the (MT) while others support the (LXX) and still others support a third version of the (OT). Which version is correct? How do these differences fit with our views on inerrancy?