A square has the same perimeter as a rectangle with a length of 12 cm and a width of 8 cm. What is the side length of the square?
一个正方形与一个长12cm，宽8cm的长方形的周长相等，这个正方形的边长是多少．
<gadget id="calculator">12 + 8</gadget>
<output>20</output>

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

<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<result>10</result>