The upper base of an isosceles trapezoid is 5 cm, the lower base is 8 cm, and the waist length is 7 cm. How many centimeters of iron wire are needed to enclose this isosceles trapezoid?
一个等腰梯形的上底是5厘米，下底是8厘米，一个腰长是7厘米，围成这个等腰梯形要多少厘米的铁丝．
<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">5 + 8 + 14</gadget>
<output>27</output>

<result>27</result>