The ratio of the lengths of the sides of an isosceles triangle is 3:5:5, and the perimeter is 52 cm. What is the length of the base of this isosceles triangle in cm?
一个等腰三角形三边长度之比3：5：5，周长是52厘米，这个等腰三角形底边长是多少厘米．
<gadget id="calculator">3 + 5 + 5</gadget>
<output>13</output>

<gadget id="calculator">3 / 13</gadget>
<output>3/13 = around 0.230769</output>

<gadget id="calculator">52 * (3/13)</gadget>
<output>12</output>

<result>12</result>