The south wall of the classroom is 8 meters long and 3 meters wide. There are three windows of 3 square meters on the wall. Now to paint this wall, how many square meters is the area to be painted?
教室南面的墙壁，长8米，宽3米．墙上有3个3平方米的窗户．现在要粉刷这面墙壁，要粉刷的面积是多少平方米？
<gadget id="calculator">8 * 3</gadget>
<output>24</output>

<gadget id="calculator">3 * 3</gadget>
<output>9</output>

<gadget id="calculator">24 - 9</gadget>
<output>15</output>

<result>15</result>