The area of a trapezoid is 20cm**2, the height is 5cm, if the upper bottom is 2.5cm, then how many cm is the lower bottom.
一个梯形的面积是20cm**2，高是5cm，如果上底是2.5cm，那么下底是多少cm．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">20 * (2/5)</gadget>
<output>8</output>

<gadget id="calculator">8 - 2.5</gadget>
<output>5.5</output>

<result>5.5</result>