Master Li wants to paint a wall with a length of 8 meters and a width of 3 meters. There is a window with an area of 4 square meters on the wall. How many square meters is the area to be painted by Master Li?
李师傅要粉刷一块长8米，宽3米的墙壁，墙上有一扇面积4平方米的窗户．李师傅要粉刷的面积是多少平方米．
<gadget id="calculator">8 * 3</gadget>
<output>24</output>

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

<result>20</result>