GLEE sneak peek - Adele mashup: "Rumour Has It" and "Someone Like You"

In a sneak peek clip, Mercedes (Amber Riley), Santana (Naya Rivera) and the rest of the Troubletones tackle a mash-up of Adele's "Rumour Has It" and "Someone Like You," which is also the show's 300th musical performance.

Both songs are from Adele's "21" which is the biggest selling album in the world this year.