December 07, 2014 - 21:12 GMT hellomagazine.com Lauren Platt leaves the X Factor semi finals Lauren Platt was voted out of The X Factor on Sunday's semi finals, after an emotional sing off with Andrea Faustini. The 17-year-old thanked her mentor before the remaining finalists, Fleur East, Ben Haenow and Andrea Faustini came out onto the stage and were shown their three X Factor battle buses, with their faces on them. We're saying goodbye to the wonderful @laurenplatt7 thanks for being an incredible contestant Lauren. #XFactorResults pic.twitter.com/hOBhuFyr5u — The X Factor (@TheXFactor) December 7, 2014 You're going to get on them right now and begin campaigning," said Dermot O'Leary. The night started with an outstanding performance by America’s X Factor, Fifth Harmony who sang Boss, before last year’s winner, Sam Bailey, returned to the stage. The time then came for Dermot to announce who would be making it to the X Factor final. "I pledge allegiance to my independent girls in here" 🙌 Thanks for Bo$$ing the stage @FifthHarmony #XFactorResults pic.twitter.com/2b4VNisot0 — The X Factor (@TheXFactor) December 7, 2014 Fleur East was the first act to have a place in the final before Ben Haenow was sent through to next week’s show.Andrea Faustini and Lauren Platt prepared to sing in the final sing off of the competition. There's some tense moments backstage with @AndreaFaustini1 + @laurenplatt7 preparing for the sing off #XFactorResults pic.twitter.com/V9cDdB5wXI — The X Factor (@TheXFactor) December 7, 2014 Let it Go’s Idina Mensel and Michael Buble then sang their first live performance of Baby It's Cold Outside. Lauren was first to perform, singing Faith Hill's There You'll Be, before Andrea sang Jessie J's Who You Are. In the end, Cheryl Cole saved her act, Lauren before Louis Walsh, Simon Cowell and Mel B saved Andrea.Tune in next Saturday to find out who will be crowned the X Factor's 2014 winner.