What is the area of a trapezoid whose upper base is 6 meters, lower base is 8 meters, and height is 3.5 meters?
一个上底是6米，下底是8米，高是3.5米的梯形，面积是多少平方米．
<gadget id="calculator">6 + 8</gadget>
<output>14</output>

<gadget id="calculator">3.5 / 2</gadget>
<output>1.75</output>

<gadget id="calculator">14 * 1.75</gadget>
<output>24.5</output>

<result>24.5</result>