To help you out Hannah, i believe the "LXX" is also called the Septuagint:
Septuagint - Wikipedia, the free encyclopediaThe Septuagint derives its name from Latin versio septuaginta interpretum,"translation of the seventy interpreters," (Greek: ἡ μετάφρασις τῶν ἑβδομήκοντα, hē metáphrasis tōn hebdomēkonta), "translation of the seventy ". The title refers to a legendary account in the pseudepigraphic Letter of Aristeas of how seventy-two Jewish scholars were asked by the Greek King of Egypt Ptolemy II Philadelphus in the 3rd century BCE to translate the Torah (or Pentateuch) from Biblical Hebrew into Greek for inclusion in the Library of Alexandria.
As narrated by Philo of Alexandria, 72 Jewish translators were enlisted to complete the translation while kept in separate chambers. They all produced identical versions of the text in seventy-two days. This story underlines the fact that some Jews in antiquity wished to present the translation as authoritative. A version of this legend is found in the Tractate Megillah of the Babylonian Talmud (pages 9a-9b), which identifies fifteen specific unusual translations made by the scholars. Only two of these translations are found in the extant LXX.