The sum of the interior angles of a polygon is 900°, what is the number of sides?
一个多边形的内角和是900°，它的边数是多少．
<gadget id="calculator">900 / 180</gadget>
<output>5</output>

<gadget id="calculator">5 + 2</gadget>
<output>7</output>

<result>7</result>