The area of a trapezoid is 480 square centimeters, the height is 12 centimeters, the upper base is 30 cm, and the lower base is how many centimeters.
一个梯形的面积是480平方厘米，高是12厘米，上底是30厘米，下底是多少厘米．
<gadget id="calculator">2 / 12</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">480 * (1/6)</gadget>
<output>80</output>

<gadget id="calculator">80 - 30</gadget>
<output>50</output>

<result>50</result>