The upper base of an isosceles trapezoid is 3 cm, the lower base is 5 cm, and its circumference is 16 cm, what is its waist length in cm?
一个等腰梯形的上底是3厘米，下底是5厘米，且它的周长是16厘米，它的腰长是多少厘米？
<gadget id="calculator">16 - 3 - 5</gadget>
<output>8</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<result>4</result>