The upper base of an isosceles trapezoid is 8 cm long, the lower base is 12 cm long, and one side is 18 cm long. What is its perimeter?
一个等腰梯形的上底长8厘米，下底12厘米，一条腰长18厘米，它的周长是多少．
<gadget id="calculator">18 * 2</gadget>
<output>36</output>

<gadget id="calculator">8 + 12 + 36</gadget>
<output>56</output>

<result>56</result>