rectangle, if its length remains the same, but its width is increased by 4 meters, its area will increase by 36 square meters. At this time, it just turns into a square. What is the area of the original rectangle in square meters?
一个长方形，如果它的长不变，宽增加4米，面积就增加36平方米，这时正好转变成正方形，原来长方形的面积是多少平方米．
<gadget id="calculator">36 / 4</gadget>
<output>9</output>

<gadget id="calculator">9 - 4</gadget>
<output>5</output>

<gadget id="calculator">9 * 5</gadget>
<output>45</output>

<result>45</result>