The lower base of a trapezoid is three times the upper base. If the upper base is increased by 7 cm and the lower base is decreased by 1 cm, the trapezoid becomes a square. What is the original area of the trapezoid in square centimeters?
一个梯形的下底是上底的3倍，如果上底增加7厘米，下底减少1厘米，这个梯形就能变成一个正方形，则这个梯形原来的面积是多少平方厘米．
<gadget id="calculator">7 + 1</gadget>
<output>8</output>

<gadget id="calculator">3 - 1</gadget>
<output>2</output>

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

<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">4 + 12</gadget>
<output>16</output>

<gadget id="calculator">4 + 7</gadget>
<output>11</output>

<gadget id="calculator">11 / 2</gadget>
<output>11/2 = around 5.5</output>

<gadget id="calculator">16 * (11/2)</gadget>
<output>88</output>

<result>88</result>