The land in front of Wang Dabai's house is surrounded by a 55-meter-long courtyard, which is 15 meters from the wall of the house. What is the area of this long courtyard?
王大柏房前的地一道55米的围，成了一个长方院子其中面是房屋的墙15米，这个长院的面积是多少？
<gadget id="calculator">2 * 15</gadget>
<output>30</output>

<result>30</result>