The lower base of a trapezoid is 6 cm. If its upper base is increased by 2 centimeters, a parallelogram is obtained, and its area is increased by 6 square centimeters. What is the area of the original trapezoid?
一个梯形的下底是6厘米．如果将它的上底增加2厘米，就得到一个平行四边形，它的面积就增加6平方厘米．原来的梯形的面积是多少．
<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">6 * 1</gadget>
<output>6</output>

<gadget id="calculator">6 - 2</gadget>
<output>4</output>

<gadget id="calculator">4 + 6</gadget>
<output>10</output>

<gadget id="calculator">2 / 2 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">10 * 6 * (1/2)</gadget>
<output>30</output>

<result>30</result>