The width of a rectangle remains the same. After the length is increased by 4 meters, the area is increased by 20 square meters. What is the original width of the rectangle?
一个长方形的宽不变，长增加4米后，面积增加20平方米，原来长方形的宽是多少？
<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<result>5</result>