Its shares were up 27 cents, or 6 percent, at $4.75 in premarket trading.
Sales at Arby's North American restaurants open at least 15 months fell 5.9 percent in its third fiscal quarter, following a 7.4 percent decline in the second quarter.
Nelson Peltz, the company's chairman and largest shareholder, said in a statement that Wendy's is the fast food company's key driver of momentum. Peltz' Trian Fund Management LP owns 18.3 percent of Wendy's/Arby's shares, according to Thomson Reuters data.
Executives said in November they asked Peltz to make a quick decision on a takeover inquiry it received about Wendy's/Arby's in June so the company could resume share buybacks.
Wendy's and Arby's merged in 2008 in a $2 billion deal. They are both trailing behind McDonald's Corp
Wendy's/Arby's said UBS Investment is assisting in the sales process.
(Reporting by Phil Wahba in New York and Nivedita Bhattacharjee in Bangalore; Editing by Derek Caney)