Saving the quarians and the geth is dependent on a points system based on your actions in ME2 and 3 leading up to that scene, you need a total of 5 points to save them both. - Rewrote the Heretics (0 points) - Destroyed the Heretics (+2 points) - Tali is NOT exiled (+2 points) - Tali has been exiled/did not do the Loyalty Mission (0 points) - Resolved Legion/Tali conflict either using the Paragon or Renegade options (+1 point) - N7 Mission: Saved Admiral Zaal'Koris vas Kwib Kwib on Rannoch (+1 point) - N7 Mission: Destroy Geth Squadron on Rannoch (+1 point) - Completed Legion's Mission in ME3 (or no peace) You also need to have filled up 4 bars of your reputation.