A rectangular swimming pool has a perimeter of 140 meters and a length of 50 meters, what is its width in meters?
一个长方形游泳池的周长是140米，长是50米，它的宽是多少米？
<gadget id="calculator">140 / 2</gadget>
<output>70</output>

<gadget id="calculator">70 - 50</gadget>
<output>20</output>

<result>20</result>