Each exterior angle = 180^o – 150^o = 30^o

Total sum of the exterior angles is 360^o

${{30}^{\circ }}n={{360}^{\circ }}\text{   (}n\text{ is the number of sides of the polygon)}$

$n=\frac{{{360}^{\text{o}}}}{{{30}^{\text{o}}}}=12$

The polygon is has 12 sides