One wall in the living room of Uncle Zhang’s house is 9 meters long and 3 meters wide. The area of doors and windows on this wall is 4 square meters. Now this wall is going to be painted, how much square meter is the area to be painted?
张叔叔家的客厅的一面墙长9米，宽3米，这面墙上的门窗面积是4㎡，现在要粉刷这面墙，要粉刷的面积是多少㎡？
<gadget id="calculator">9 * 3</gadget>
<output>27</output>

<gadget id="calculator">27 - 4</gadget>
<output>23</output>

<result>23</result>