A rectangle has a perimeter of 18 cm and a length of 7 cm. What is the width in cm?
一个长方形，周长是18厘米，长是7厘米，宽是多少厘米？
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">9 - 7</gadget>
<output>2</output>

<result>2</result>