Use a 20 decimeter long iron wire to form a rectangle with a length of 7 decimeters and how many decimeters wide?
用一根长20分米的铁丝围成一个长方形，长为7分米，宽是多少分米？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 - 7</gadget>
<output>3</output>

<result>3</result>