You know you've got a shot in the music business when Christina Aguilera is rooting for her you -- and that's exactly what happened last night for 17-year-old "The Voice" contestant Alessandra Guercio. Adam Levine had Alessandra and 17-year-old Kayla Nevarez battle through their dynamic rendition of Katy Perry's "Wide Awake." All four judges agreed that both girls were excellent singers; Alessandra's gravelly twang and Kayla's sweet vibrato played off each other perfectly.