// ------------------------------------------------------------------- //
//  Muted
// ------------------------------------------------------------------- //

%muted{
  opacity: .5;
  filter: alpha(opacity=50);
}
// ------------------------------------------------------------------- //
//  Muted
// ------------------------------------------------------------------- //

@mixin muted($mute-amt){
  opacity: $mute-amt;
  filter: alpha(opacity=($mute-amt * 100));
}

Remove muted extend, replace with mixin
Remove muted extend, replace with mixin
