The perimeter of an isosceles triangle is 20 cm and the length of one side is 8 cm. What is the length of the base of this triangle in centimeters?
一个等腰三角形的周长是20厘米，一条腰长8厘米．那么这个三角形的底边长是多少厘米？
<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<gadget id="calculator">20 - 16</gadget>
<output>4</output>

<result>4</result>