The length of the base of an isosceles triangle is 15 cm, and one of its sides is 5 cm shorter than the base. What is the perimeter of the triangle in cm?
一个等腰三角形的底边长是15厘米，它的一条腰长比底边短5厘米，这个三角形的周长是多少厘米？
<gadget id="calculator">15 - 5</gadget>
<output>10</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">15 + 20</gadget>
<output>35</output>

<result>35</result>