Xiaohua uses a 20 cm long iron wire to form a rectangle with a width of 3 cm. What is the length of this rectangle in cm?
小华用一根长20厘米的铁丝围成一个宽是3厘米的长方形，这个长方形的长是多少厘米．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

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

<result>7</result>