The area of a trapezoid is 80 square decimeters, the height is 8 decimeters, the length of the upper base is 9 decimeters, and the length of the lower base is how many decimeters.
一个梯形的面积是80平方分米，高是8分米，其中上底长9分米，下底长多少分米．
<gadget id="calculator">2 / 8</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">80 * (1/4)</gadget>
<output>20</output>

<gadget id="calculator">20 - 9</gadget>
<output>11</output>

<result>11</result>