help with geometry

Area of triangle ABC 

This question is WRONG!!!

[ABC] cannot be more than 200 square units!!!

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Here's the corrected question:

Triangle ABC is isosceles with AB = BC.  If AB = 20 and [ABC] = 180, then find the perimeter of triangle ABC.

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[ABC] = 180           AB = BC = 20

FE = [ABC] / BC = 9

x/9 = 9/(20-x)

x = 10 - √19

AC = 2[sqrt(x² + 9²)] ≈ 21.244

Perimeter ≈ 61.244