A regular hexagon is a polygon with six sides.
The sum of the interior angles of a polygon is calculated as: (2n-4)90
where 'n' represents the number of sides of the polygon.
from the question provided, each interior angle of the regular hexagon is (15x-45). Therefore, the sum of the interior angles of the regular hexagon will be given by 6(15x-45).

Hence, the value of x is 11