A rectangle with a length of 9 cm and a width of 3 cm is formed with a piece of iron wire. If the wire is used to form a square, what is the side length of the square in cm?
用一根铁丝恰好围成一个长9厘米，宽3厘米的长方形，如果把这根铁丝围成一个正方形，这个正方形的边长是多少厘米．
<gadget id="calculator">9 + 3</gadget>
<output>12</output>

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

<gadget id="calculator">12 * (1/2)</gadget>
<output>6</output>

<result>6</result>