The upper base of an isosceles trapezoid is 6 cm, the lower base is 8 cm, and the length of one side is 7 cm. How many centimeters of iron wire is needed to enclose such an isosceles trapezoid?
一个等腰梯形的上底是6厘米，下底是8厘米，一条腰长是7厘米．围成这样一个等腰梯形至少需要多少厘米长的铁丝？
<gadget id="calculator">8 + 6 + 7 + 7</gadget>
<output>28</output>

<result>28</result>