WASHINGTON (AP) — Average U.S. rates on fixed mortgages declined this week after two weeks of increases, keeping home-buying affordable.Mortgage buyer Freddie Mac said Thursday that the average rate on the 30-year loan fell to 4.22 percent from to 4.35 percent last week. The average on the 15-year fixed mortgage dipped to 3.27 percent from 3.35 percent.Rates had spiked over the summer and reached a two-year high in July on speculation that the Federal Reserve would slow its bond purchases later this year. But the Fed held off in September and now appears poised to wait at least a few more months to see how the economy performs.