The cabbage field in the farm is an isosceles trapezoid with a perimeter of 35 cm, of which the lower base is 7 cm and the upper base is 6 cm. What is the length of the waist in centimeters?
农场里的白菜地是一个等腰梯形，它的周长是35厘米，其中下底是7厘米，上底是6厘米．腰的长度是多少厘米？
<gadget id="calculator">35 - 7 - 6</gadget>
<output>22</output>

<gadget id="calculator">22 / 2</gadget>
<output>11</output>

<result>11</result>