What is the area of a trapezoid whose upper base is 3 meters, lower base is 5 meters, and height is 2 meters?
一个梯形上底3米，下底5米，高2米，面积是多少．
<gadget id="calculator">3 + 5</gadget>
<output>8</output>

<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">8 * 1</gadget>
<output>8</output>

<result>8</result>