The sum of “green” interior angles is 360° (similar for the “blue” angles). Therefore, the sum of the colored angles is 720°.
The sum of interior angles of a triangle is 180°. There are 5 triangles, so the sum of all of their interior angles is 5*180°=900°.
Finally, subtract 720° from 900° to find the sum of interion angles of the star.
900°-720°=180°
The sum of the interior angles of a 5-point star is 180°. And it’s true for all 5-point stars.