You can
put this solution on YOUR website!I'm assuming that you mean a "regular" polygon!
The measure of an interior angle, A, of a regular polygon of N sides is given by:

Substitute A = 120 degrees.

Multiply both sides by N.

Subtract 120N from both sides.

Add 360 to both sides.

Finally, divide both sides by 60.
The regular polygon has 6 equal sides and is called a hexagon.