Ruth admits she feels "lucky" to be on the show, after a poor audition earlier in the series.
Only Jessie J turned around for her, with the other coaches mocking Ruth's out of tune performance.
The teenager admits: "I feel luck to be here right now. I feel as though I have to prove myself more than anyone else, and I’m going to bring it.”
Ben Kelly however is showing no signs of nerves, saying: "I’m still as confident as I was but I will not underestimate the competition."
The pair goes on to perform I Wanna Dance With Somebody together for Jessie and the other coaches.
Find out who makes the live shows at 7:30PM on BBC One tonight.