The upper base of a trapezoid is 6 cm, 2 cm shorter than the lower base, and the height is 4 cm. What is its area in square centimeters?
一个梯形的上底是6厘米，比下底少2厘米，高是4厘米，它的面积是多少平方厘米．
<gadget id="calculator">6 + 2</gadget>
<output>8</output>

<gadget id="calculator">6 + 8</gadget>
<output>14</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">14 * 2</gadget>
<output>28</output>

<result>28</result>