the complete question in the attached figure
we know that
An exterior angle is one that has its vertex at an outer point of the circumference.
The measure of the external angle is the semi-difference of the arcs that it covers.
in this problem the external angle is ∡(9x-5)°
and
the semi-difference of the arcs that it covers is (1/2)*(158°-64°)=47°
then
(9x-5)=47-------> 9x=47+5----------> 9x=52--------> x=5.78°
the answer is
x=5.78°