What is the number of diagonals in a polygon of $12$ sides?

Find the number of sides of a regular polygon whose each exterior angle measure: $40°$

Find the number of sides of a regular polygon whose each exterior angle measure: $36°$

Find the number of sides of a regular polygon whose each exterior angle measures: $72°$

Find the number of sides of a regular polygon whose each exterior angle measures: $30°$

In the given figure, find the angle measure $x$.

Find the angle measure $x$ in the given figure.