Solution explained: To find the solution to this puzzle, it is important to recognize that Black's King is behind three of it's own Pawns and thus could be checkmated on the "back rank" of the board with a Rook or a Queen. And then it is important to notice that White's Queen and two Rooks are all pointing at the same e8 square that is only defended twice (by the Black Rook on a8 and the Black Knight on f6). Then all White has to do is move the Queen or Rook to e8, get captured, then recapture with a queen or rook that is left, get captured again, and then finally recapture with the final piece that can on e8, delivering a back rank checkmate to the Black King.