The perimeter of a rectangle is 400 meters, the width is 30 meters, what is the length?
一个长方形的周长是400米，宽是30米，长是多少米？
<gadget id="calculator">400 / 2</gadget>
<output>200</output>

<gadget id="calculator">200 - 30</gadget>
<output>170</output>

<result>170</result>