Try doing a simple drawing, you know the relation of pressure to height so its only a case of applying the figure in the correct direction. QFE wil be lower than QNH unless the airfield is below sea level.
A Flight level is measured relative to a pressure datum of 1013 (forget the 0.2) If the QNH is 1013 the altitude will be the same as the flight level, if the QNH is lower, the altitude will be lower.