The perimeter of a rectangular vegetable field is 30 meters, if its length is 10 meters, what is its width in meters
一个长方形菜地的周长是30米，如果它的长是10米，那么它的宽是多少米
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">15 - 10</gadget>
<output>5</output>

<result>5</result>