The perimeter of an isosceles triangle is 50 decimeters and the length of the base is 20 decimeters. What is the length of one of its sides?
一个等腰三角形的周长是50分米，底边长20分米，它的一条腰长是多少？
<gadget id="calculator">50 - 20</gadget>
<output>30</output>

<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<result>15</result>