The perimeter of an isosceles trapezoid is 32 cm, the sum of the upper and lower bases is 12 cm, what is the waist length?
一个等腰梯形的周长是32厘米，上下底的和是12厘米，腰长是多少．
<gadget id="calculator">32 - 12</gadget>
<output>20</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<result>10</result>