A trapezoid, if the upper base is reduced by 3 meters, becomes a triangle, and the area is reduced by 7.5 square meters, and if the upper base is increased by 3 meters, it becomes a parallelogram. So what is the area of the original trapezoid?
一个梯形，如果上底减少3米就成了一个三角形，并且面积减少了7.5平方米，如果上底增加3米，就变成了一个平行四边形．那么原来梯形的面积是多少？
<gadget id="calculator">3 + 3</gadget>
<output>6</output>

<gadget id="calculator">3 + 6</gadget>
<output>9</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">7.5 * (2/3)</gadget>
<output>5</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">9 * (5/2)</gadget>
<output>45/2 = around 22.5</output>

<result>45/2 = around 22.5</result>