If the perimeter of an isosceles triangle is 60 cm and the ratio of its two sides is 2:5, what is the length of the waist of the triangle?
一个等腰三角形周长为60厘米，它的两条边的比为2：5，则这个三角形的腰长多少．
<gadget id="calculator">2 + 5 + 5</gadget>
<output>12</output>

<gadget id="calculator">5 / 12</gadget>
<output>5/12 = around 0.416667</output>

<gadget id="calculator">60 * (5/12)</gadget>
<output>25</output>

<result>25</result>