The school has to paint the walls and ceiling of a classroom. It is known that the length of the classroom is 8 meters, the width is 7 meters, and the height is 3 meters. The area of the blackboard doors and windows is 3.0 square meters. How many square meters is the area to be painted?
学校要粉刷一间教室的四壁和天花板．已知教室的长是8米，宽7米，高是3米，扣除黑板门窗的面积3.0平方米，要粉刷的面积是多少平方米？
<gadget id="calculator">8 * 7</gadget>
<output>56</output>

<gadget id="calculator">8 * 3</gadget>
<output>24</output>

<gadget id="calculator">7 * 3</gadget>
<output>21</output>

<gadget id="calculator">24 + 21</gadget>
<output>45</output>

<gadget id="calculator">45 * 2</gadget>
<output>90</output>

<gadget id="calculator">90 - 3</gadget>
<output>87</output>

<gadget id="calculator">56 + 87</gadget>
<output>143</output>

<result>143</result>