The upper base of a trapezoid is 5 cm, the lower base is 12 cm, and the height is 0.8 decimeters. What is its area?
一个梯形的上底是5厘米，下底是12厘米，高是0.8分米，它的面积是多少．
<gadget id="calculator">5 + 12</gadget>
<output>17</output>

<gadget id="calculator">0.8 / 2</gadget>
<output>0.4</output>

<gadget id="calculator">17 * 0.4</gadget>
<output>6.8</output>

<result>6.8</result>