A rectangle and a square have the same perimeter. The length of the rectangle is 10 decimeters and the width is 8 decimeters. What is the side length of the square?
一个长方形和一个正方形，它们的周长相等，长方形的长是10分米，宽是8分米，正方形的边长是多少分米？
<gadget id="calculator">10 + 8</gadget>
<output>18</output>

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

<gadget id="calculator">18 * (1/2)</gadget>
<output>9</output>

<result>9</result>