The upper base of a trapezoid is 12 cm long. If the upper base is extended by 4 cm, it becomes a parallelogram with an area increased by 36 cm2. What is the area of the trapezoid?
一个梯形的上底长12厘米，如果上底延长4厘米，就成为一个平行四边形，面积也比原来增加36平方厘米．梯形的面积是多少？
<gadget id="calculator">12 + 12 + 4</gadget>
<output>28</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">36 * (1/2)</gadget>
<output>18</output>

<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">28 * 9</gadget>
<output>252</output>

<result>252</result>