If the upper base of a trapezoid is extended by 3 centimeters, the area increases by 12 square centimeters, and the trapezoid becomes a square. Do you know what is the area of this trapezoid?
一个梯形如果上底延长3厘米，面积就增加12平方厘米，这个梯形就变成了正方形．你知道这梯形的面积是多少吗？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">12 * (2/3)</gadget>
<output>8</output>

<gadget id="calculator">8 * 8</gadget>
<output>64</output>

<gadget id="calculator">64 - 12</gadget>
<output>52</output>

<result>52</result>