Three poles are used to create the frame for a tent. The front of the tent is an isosceles triangle with AB congruent to BC. The length of the base is 1.5 times the length of the sides. The perimeter of the trangle is 21 ft. Find each side length.

I think that the side length AC = 10.5 ft and the side lengths AB and BC are 7 ft each. If you know the right answers, please tell me if I'm right.