There is a "hollow phalanx" with 3 layers of people standing. 10 people stand on each side of the outermost layer. Do the math: How many people are there in total?
有一个站了3层人的"中空方阵"．最外层每边站10人．算一算：全阵共站了多少人？
<gadget id="calculator">10 - 3</gadget>
<output>7</output>

<gadget id="calculator">7 * 3 * 4</gadget>
<output>84</output>

<result>84</result>