right-angled trapezoid, the ratio of the length of the upper base to the lower base is 3:5, if the upper base is increased by 7 cm and the lower base is decreased by 1 cm, it becomes a square, what is the area of the trapezoid in square centimeters?
一个直角梯形，上底与下底的长度比是3：5，如果把上底增加7厘米，下底减少1厘米，就变成一个正方形，这个梯形的面积是多少平方厘米．
<gadget id="calculator">7 + 1</gadget>
<output>8</output>

<gadget id="calculator">5 - 3</gadget>
<output>2</output>

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

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

<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<gadget id="calculator">12 + 20</gadget>
<output>32</output>

<gadget id="calculator">12 + 7</gadget>
<output>19</output>

<gadget id="calculator">19 / 2</gadget>
<output>19/2 = around 9.5</output>

<gadget id="calculator">32 * (19/2)</gadget>
<output>304</output>

<result>304</result>