The area of a trapezoid is 24 square centimeters, the upper base is 3 cm, and the height is 4 cm. What is the lower base?
一个梯形面积是24平方厘米，上底是3厘米，高是4厘米，那么下底是多少．
<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">24 * (1/2)</gadget>
<output>12</output>

<gadget id="calculator">12 - 3</gadget>
<output>9</output>

<result>9</result>