The performers booked their place in the next round on tonight's live results episode of the NBC competition.
Sharon was thrilled when Poplyfe and Landau wee brought on stage together and cleared to proceed, saying: "I was really really worried to see these two going head to head with each other... I am absolutely delighted for both of you because you're two different musical genres, but there is a place for each one of you in the music industry today and I feel so strongly that both of you are going to be in the final."
Howie was similarly ecstatic about Lys Agnes's success, saying: "America did themselves right. You are absolutely beautiful. You're gorgeous, your voice is gorgeous. You did it, you deserve to be here."
The third batch of 12 acts from this season's Top 48 performed for the judges and voting public last night as they competed for the $1 million (£619,069) prize and the chance to headline a show in Las Vegas.
Their success means that Purrfect Angelz, Ian Johnson, Summerwind Skippers, Monet, The Captain & Maybelle, Mauricio Herrera, Sh'Boss Boys and Seth Grabel were eliminated from the competition and sent home empty handed.
Snap Boogie, Sandou Trio Russian Bar, Anna Graceman, Miami All-Stars, Silhouettes, Steven Retchless, Daniel Joseph Baker and Smage Bros. Riding Team have already gone forward to the semi-finals.
Tonight's instalment also featured performances from Stevie Nicks, who took to the stage twice to perform her new single 'For What It's Worth' and her classic hit 'Edge of Seventeen'.
Former America's Got Talent top three group Fighting Gravity also lit up the stage with their laser dance and choreography routine.
America's Got Talent continues next Tuesday at 9/8c on NBC.
> America's Got Talent: Quarter Final 3 recap