The perimeter of an isosceles triangle is 28 decimeters, and the ratio of one waist to the base is 5:4. What is the base of this isosceles triangle?
一个等腰三角形周长是28分米，其中一条腰与底边的比是5：4，这个等腰三角形的底边是多少．
<gadget id="calculator">5 + 5 + 4</gadget>
<output>14</output>

<gadget id="calculator">4 / 14</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">28 * (2/7)</gadget>
<output>8</output>

<result>8</result>