Puzzles - Missing letters puzzles

Starting with the top letter in each star, and moving clockwise around the others, letters advance through the alphabet in steps of 8 for the left hand star, 9 for the central star, and 10 for the right hand star.

Working from left to right, following the zig-zag pattern of the line, letters move through the alphabet skipping 15 letters, then 14, then 13 etc.

Split the diagram horizontally and vertically into 4 quarters. A sequence of letters is written in each quarter, following the alphabetic order, 3 letters at a time, starting with the upper left quarter. Add 2 to the values of each letter to give the letters in the next quarter clockwise, then 3, then 4.