If the length of a rectangle is increased by 3cm, the area will be increased by 15cm**2. What is the original width of the rectangle in cm?
一个长方形，把它的长增加3cm，面积就增加15cm**2，原来长方形的宽是多少cm．
<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<result>5</result>