Use a piece of iron wire to form a square with a side length of 20 cm, and then straighten it to form a rectangle again. The width of this rectangle is 12 cm, and what is the length in cm?
用一根铁丝围成一个边长是20厘米的正方形，再把它拉直重新围成一个长方形，这个长方形的宽是12厘米，长是多少厘米？
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<gadget id="calculator">40 - 12</gadget>
<output>28</output>

<result>28</result>