Puzzles - Missing letters puzzles

Answer

:

P

Explanation

:

Starting in the top left corner and moving clockwise in a spiral towards the centre, letters follow the alphabetic sequence, skipping 5 letters at a time, written in alternate squares of the diagram.

Answer

:

C

Explanation

:

The sum of the numerical values of pairs of letters, opposite each other in the diagram, is always 20 (the numerical value of the central letter).

Answer

:

M

Explanation

:

In each diagram, start with the upper left box, and move anti-clockwise around the others. Letters advance through the alphabet in steps of 7 for the upper left diagram, 8 for the middle, then 9, then 10.