rectangle is 10 meters long and 8 meters wide. Its perimeter is equal to that of a square. What is the side length of the square?
长方形长10米，宽8米，它的周长和一个正方形的周长相等，这个正方形的边长是多少米？
<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>