Answer:
30°
Explanation:
You want the measure of angle AEF in regular hexagon ABCDEF.
Interior angles
The interior angles of a regular hexagon are ...
180° -(360°/6) = 120°
Angle AEF is 90° less than this, so is ...
angle AEF = 120° -90°
angle AEF = 30°
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Additional comment
Angle AEF is also a base angle of isosceles triangle AEF, which has angle F = 120°. The base angles are (180° -120°)/2 = 30°.