Hong Hong uses an 18 cm long iron wire to form a 5 cm long rectangle. Please calculate the width of this rectangle.
红红用一根长18厘米的铁丝围成一个长为5厘米的长方形，请你算出这个长方形的宽．
<gadget id="calculator">18 / 2</gadget>
<output>9</output>

<gadget id="calculator">9 - 5</gadget>
<output>4</output>

<result>4</result>