There is a rectangular fish pond in Guangming Village with a circumference of 60 meters and a length of 18 meters. How many meters is this fish pond wide?
光明村有一个长方形的鱼塘周长是60米，长有18米，这个鱼塘的宽有多少米？
<gadget id="calculator">60 / 2</gadget>
<output>30</output>

<gadget id="calculator">30 - 18</gadget>
<output>12</output>

<result>12</result>