One wall of a conference room is 8 meters long and 3 meters wide. There is a window on the wall with an area of 4 square meters. Now we want to paint this wall, how many square meters should the painted area be?
一间会议室的一面墙长8米，宽3米．墙上有一面窗，面积为4平方米．现在要粉刷这一面墙，粉刷的面积应是多少平方米？
<gadget id="calculator">8 * 3</gadget>
<output>24</output>

<gadget id="calculator">24 - 4</gadget>
<output>20</output>

<result>20</result>