The area of a trapezoid is 28 square centimeters, its upper base is 5 cm, and its lower base is 2 cm. What is its height in cm?
一个梯形的面积是28平方厘米，它的上底是5厘米，下底是2厘米，它的高是多少厘米．
<gadget id="calculator">5 + 2</gadget>
<output>7</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">28 * (2/7)</gadget>
<output>8</output>

<result>8</result>