A classroom is 9 meters long, 6 meters wide, and 4 meters high. The walls and ceiling of the classroom need to be painted. Deduct 19.5 square meters of doors and windows, and find the area to be painted.
一个教室长9米、宽6米、高4米，要粉刷教室的四壁和顶面．扣除门窗19.5平方米，求粉刷面积．
<gadget id="calculator">9 * 6</gadget>
<output>54</output>

<gadget id="calculator">6 * 4 * 2</gadget>
<output>48</output>

<gadget id="calculator">9 * 4 * 2</gadget>
<output>72</output>

<gadget id="calculator">54 + 48 + 72</gadget>
<output>174</output>

<gadget id="calculator">174 - 19.5</gadget>
<output>154.5</output>

<result>154.5</result>