at the rules has an example about scoring of the cathedral.a carthedral gives 3 points per tile(complete city)and pennant.
at the manuals example the score said that is 24 for the blue player.is this correct?because i count 27.
It is correct at 24 points. You score per TILE. The piece to the left of the cathedral is one "tile" even though it has two "sections" - this is probably why you are coming up with 27 and why you are incorrect.