The exterior angles to any convex polygon sum to 360 degrees in measure, so that for a regular dodecagon (12-gon) each exterior angle has measure
[tex]\dfrac{360^\circ}{12}=30^\circ[/tex]
Exterior angles are complementary to interior angles, which means each interior angle has measure
[tex]180^\circ-30^\circ=\boxed{150^\circ}[/tex]
