After the side length of a square is enlarged, the area is enlarged to 9 times of the original, and the side length of the enlarged square is 12 cm. What is the original side length of this square?
一个正方形边长扩大后，面积扩大为原来的9倍，扩大后正方形的边长为12厘米．这个正方形原来的边长是多少厘米？
<gadget id="calculator">12 / 3</gadget>
<output>4</output>

<result>4</result>