The perimeter of a triangle is 66 cm, the length of side a is 30 cm, and the length of side b is 18 cm. What is the length of side c in cm? What kind of triangle is this?
一个三角形的周长是66厘米，其中a边的长是30厘米，b边的长是18厘米，求c边的长是多少厘米？这是一个什么三角形？
<result>12</result>