If the width of the rectangle increases by 1 decimeter, the area increases by 3 square decimeters, and it is just called a square, then what is the area of the original rectangle?
如果长方形的宽增加1分米，面积就增加3平方分米，并且正好称为正方形，那么原来这个长方形的面积是多少平方分米．
<gadget id="calculator">3 / 1</gadget>
<output>3</output>

<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<result>6</result>