+171 are you asking for confirmation i dont know?
we have $9x+x=180 \therefore x=18$
since 18 is the exterior angle, it means the interior angle is 162.
that gives you $ 162n\:=\:180n\:−\:360\: $which implies that $ n=20 $ so you are correct $\overset{. \: .}{\smile} $
