The area of a trapezoid is 24cm**2, the length of the lower base is 7cm, the height is 4cm, what is the length of the upper base in cm?
一个梯形的面积是24cm**2，下底长7cm，高是4cm，上底长多少cm．
<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 - 7</gadget>
<output>5</output>

<result>5</result>