right-angled trapezoid, if the upper base is extended by 5 cm, the area will increase by 25 square centimeters and become a square. What is the area of the original trapezoid in square centimeters?
一个直角梯形，如果把上底延长5厘米，面积就增加25平方厘米，而且变成一个正方形，原来梯形的面积是多少平方厘米．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">10 * 10</gadget>
<output>100</output>

<gadget id="calculator">100 - 25</gadget>
<output>75</output>

<result>75</result>