Mortgage rates were little changed ahead of the Federal Reserve’s key rate decision next week, mortgage buyer Freddie Mac said Thursday. The 30-year fixed rate mortgage averaged 3.90% in the week ending Sept. 10, up from 3.89. The 15-year fixed-rate mortgage averaged 3.10%, up from 3.09%, and the 1-year Treasury-indexed adjustable rate mortgage averaged 2.63%, up from 2.62%. The 5-year Treasury-indexed hybrid ARM averaged 2.91%, down from 2.93%.