A classroom is 8m long, 4m wide, and 3m high. It is necessary to paint the roof and surrounding walls of the teacher. The area excluding doors, windows and blackboards is 20 square meters. What is the area to be painted?
一间教室长8m、宽4m、高3m，要粉刷教师的屋顶和四周墙壁，除去门窗和黑板的面积20平方米，粉刷的面积是多少？
<gadget id="calculator">8 * 4</gadget>
<output>32</output>

<gadget id="calculator">8 * 3 * 2</gadget>
<output>48</output>

<gadget id="calculator">3 * 4 * 2</gadget>
<output>24</output>

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

<gadget id="calculator">32 + 48 + 4</gadget>
<output>84</output>

<result>84</result>