What is the area of a rectangle with a perimeter of 30 meters and a length of 8 meters?
一个长方形的周长为30米，长为8米，它的面积是多少．
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">15 - 8</gadget>
<output>7</output>

<gadget id="calculator">8 * 7</gadget>
<output>56</output>

<result>56</result>