The wall in front of the classroom in Class 3 is 5 meters long and 3 meters wide. There is an electronic whiteboard on the wall with an area of 4 square meters. Now we want to paint this wall, how many square meters is the area to be painted?
三1班教室前面的墙壁，长是5米、宽是3米．墙上有一块电子白板，面积是4平方米，现在要粉刷这面墙壁，需要粉刷的面积是多少平方米？
<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">15 - 4</gadget>
<output>11</output>

<result>11</result>