The area of a trapezoid is 30 square decimeters, the height is 3 decimeters, the upper base is 8 decimeters, and the lower base is how many decimeters
一个梯形的面积是30平方分米，高是3分米，上底是8分米，下底是多少分米
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">30 * (2/3)</gadget>
<output>20</output>

<gadget id="calculator">20 - 8</gadget>
<output>12</output>

<result>12</result>