Uncle Zhang surrounded a rectangular vegetable field with an 84-meter-long fence. The length of the vegetable field is 24 meters, and how many meters is the width?
张大爷用84米长的篱笆围成一个长方形的菜地，菜地的长是24米，宽是多少米？
<gadget id="calculator">84 / 2</gadget>
<output>42</output>

<gadget id="calculator">42 - 24</gadget>
<output>18</output>

<result>18</result>