To determine the measure of an exterior angle \( x \), we generally need more information, such as the measure of an interior angle or the context of a polygon (for instance, if it's a triangle, quadrilateral, etc.).
The exterior angle of a polygon is calculated by subtracting the interior angle from 180 degrees. For example, if we denote an interior angle as \( y \), the exterior angle \( x \) can be expressed as:
\[ x = 180^\circ - y \]
If you have specific measures or if it's related to a certain shape, please provide that information so I can assist you further!