easy! but nice!
Get checkmate in 3 moves

There is no forced mate in 3, but more forcing than the solution given would have been Qxc5
The Queen can't be touched ... (Bxe5 Rc1+ Rf1 Rxf1#) and that leaves white nothing to do but "throw furniture in the way" in any of a large number of obviously futile ways.

Well, previous posters were right that this is not a forced mate in three, but you were right that the winning move is 1...Rxc3. Sr. Calero seemed to be on the right track. I think this is a forced mate in six:
1...Rxc3 2.Re1 Rc1 3.Rfe2 Rxe1+ 4.Rxe1 Qd2 5.Re2 Qxe2 and mate on move 6

That is nice. Of course with you not moving the queen who is threatened. Maybe white should look before he leaps.
The challenge here is to win the game in three moves.