The perimeter of an isosceles trapezoid is 24 centimeters. It is known that the sum of its upper and lower bases is 12 centimeters. How many centimeters is each waist of the isosceles trapezoid.
一个等腰梯形的周长是24厘米，已知它的上底和下底的和是12厘米，等腰梯形的每条腰都是多少厘米．
<gadget id="calculator">24 - 12</gadget>
<output>12</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<result>6</result>