What is the width of a rectangle with a length of 10 cm and a circumference of 30 cm?
长10厘米，周长30厘米的长方形，它的宽是多少厘米
<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">15 - 10</gadget>
<output>5</output>

<result>5</result>