A piece of iron wire forms a rectangle. The length of the rectangle is 18 decimeters and the width is 12 decimeters. Now it is necessary to form a square. What is the side length of the enclosed square?
一根铁丝围成一个长方形，长方形的长是18分米，宽12分米，现在要把它围成一个正方形，围成的正方形的边长是多少分米？
<gadget id="calculator">18 + 12</gadget>
<output>30</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">30 * (1/2)</gadget>
<output>15</output>

<result>15</result>