The school has to paint the walls and ceiling of a classroom. It is known that the length of the classroom is 6 meters, the width is 5 meters, and the height is 3 meters. The area after deducting the doors and windows is 12.5 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6米，宽5米，高是3米，扣除门窗的面积12.5平方米，要粉刷的面积是多少平方米？
<gadget id="calculator">6 * 5</gadget>
<output>30</output>

<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<gadget id="calculator">18 + 15</gadget>
<output>33</output>

<gadget id="calculator">33 * 2</gadget>
<output>66</output>

<gadget id="calculator">66 - 12.5</gadget>
<output>53.5</output>

<gadget id="calculator">30 + 53.5</gadget>
<output>83.5</output>

<result>83.5</result>