trapezoid becomes a square after its lower base is shortened by 5 cm, and its area is reduced by 20 square centimeters. What is the area of the original trapezoid in square centimeters?
一个梯形，它的下底缩短5厘米后就变成了一个正方形，且面积减少了20平方厘米，原来的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">20 * (2/5)</gadget>
<output>8</output>

<gadget id="calculator">8 + 5 + 8</gadget>
<output>21</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">21 * 4</gadget>
<output>84</output>

<result>84</result>