The height of a trapezoid is 6 cm, and the lower base is 10 cm. If the upper base is increased by 7 cm, it becomes a parallelogram. What is the area of the trapezoid in square centimeters?
一个梯形的高是6厘米，下底10厘米，如果上底增加7厘米，它就变成了一个平行四边形，这个梯形的面积是多少平方厘米．
<gadget id="calculator">10 - 7</gadget>
<output>3</output>

<gadget id="calculator">3 + 10</gadget>
<output>13</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">13 * 3</gadget>
<output>39</output>

<result>39</result>