If the width of a rectangle is extended by 4 centimeters, the area will increase by 48 square centimeters. What is the length of the original rectangle in centimeters?
把一个长方形的宽延长4厘米，面积就增加48平方厘米，原长方形的长是多少厘米？
<gadget id="calculator">48 / 4</gadget>
<output>12</output>

<result>12</result>