The perimeter of the rectangle is 20 meters, the length is 8 meters, how many meters is the width?
长方形的周长是20米，长8米，宽多少米？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 - 8</gadget>
<output>2</output>

<result>2</result>