84 cm long iron wire is used to form a cuboid with a length of 8 cm, a width of 7 cm, and a height of cm.
用84厘米长的铁丝围成一个长方体，长8cm，宽7cm，高多少cm．
<gadget id="calculator">84 / 4</gadget>
<output>21</output>

<gadget id="calculator">21 - 8 - 7</gadget>
<output>6</output>

<result>6</result>