The perimeter of an isosceles triangle is 39 cm. Its base is 10 centimeters long, how many centimeters is its waist long?
一个等腰三角形的周长是39厘米．它的底边长10厘米，一条腰长多少厘米？
<gadget id="calculator">39 - 10</gadget>
<output>29</output>

<gadget id="calculator">29 / 2</gadget>
<output>29/2 = around 14.5</output>

<result>29/2 = around 14.5</result>