The area of a trapezoid is 72 square centimeters, the height is 8 centimeters, and the upper base is 6 cm. What is its lower base?
一个梯形的面积是72平方厘米，高是8厘米，上底是6厘米，它的下底是多少．
<gadget id="calculator">2 / 8</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">72 * (1/4)</gadget>
<output>18</output>

<gadget id="calculator">18 - 6</gadget>
<output>12</output>

<result>12</result>