Answer:
30cm
Explanation:
The perimeter of the triangle is the sum of all of its sides
Since the triangle is an isosceles triangle, then AC = BC
Since AC = 3cm + 9cm = 12cm, then;
AC = BC = 12cm
For AB;
AB = 3cm + 3cm
AB = 6cm
Perimeter of the polygon = AC+BC + AB
Perimeter of the polygon = 12cm + 12cm + 6cm
Perimeter of the polygon =30cm