The area of a parallelogram and a rectangle are both 72 square centimeters. The length of the rectangle is 18 cm, which is twice the height of the parallelogram. How many centimeters is the base of the parallelogram.
一个平行四边形和一个长方形的面积都是72平方厘米．长方形长18厘米，是平行四边形高的2倍．平行四边形的底是多少厘米．
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">72 / 9</gadget>
<output>8</output>

<result>8</result>