The lower base of a trapezoid is 7 cm. If the upper base is increased by 2 cm, it becomes a square. What is the area of the trapezoid in square centimeters?
一个梯形的下底是7厘米，如果上底增加2厘米，就变成了正方形．原来这个梯形的面积是多少平方厘米？
<gadget id="calculator">7 - 2</gadget>
<output>5</output>

<gadget id="calculator">5 + 7</gadget>
<output>12</output>

<gadget id="calculator">7 / 2</gadget>
<output>7/2 = around 3.5</output>

<gadget id="calculator">12 * (7/2)</gadget>
<output>42</output>

<result>42</result>