/sci/ - Science & Math

Here with another retarded geometry question.

DE // AB, AF and BF are bisectors of the angle A and B respectively, AC = 8 and BC = 12.
How do I find the perimeter of triangle DEC?
I'm starting to get a little frustrated. I've tried with a lot of theorems, including Thales and a lot of weird proportions. I think it can be solved with a system of equations, but still can't figure out which one.
A hint or the solution would be greatly appreciated.