There is a trapezoid, if the upper base is increased by 4cm, and the lower base and height remain unchanged, then it becomes a parallelogram with an area increased by 10 square centimeters; if the upper base is decreased by 3cm. The lower base and height remain unchanged, and now it becomes a triangle. What is the area of the original trapezoid in square centimeters?
有一个梯形，如果上底增加4cm，下底和高都不变，这时就变成一个平行四边形，面积增加10平方厘米；如果上底减少3cm．下底和高都不变，这时就变成了一个三角形，原梯形的面积是多少平方厘米？
<gadget id="calculator">3 + 3 + 4</gadget>
<output>10</output>

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

<gadget id="calculator">10 * (1/2)</gadget>
<output>5</output>

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

<gadget id="calculator">10 * (5/2)</gadget>
<output>25</output>

<result>25</result>