The lower base of a right-angled trapezoid is 15 cm. If the lower base is shortened by 3 cm, the original trapezoid becomes a square. What is the area of the original trapezoid in square centimeters?
一个直角梯形的下底是15厘米，如果下底缩短3厘米，原来的梯形就变成了正方形．原来梯形的面积是多少平方厘米．
<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">12 + 15</gadget>
<output>27</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">27 * 6</gadget>
<output>162</output>

<result>162</result>