Puzzles - Missing letters puzzles

Converting each letter to its numerical value and reading each line as a 2 digit number, the numbers follow the sequence of multiples of 6, from 36 to 54.

Starting with the left hand circle in the top row, add 4 to the numerical value of each letter and write the letter with this value in the corresponding segment of the lower left circle. Continue this pattern, adding 5 to the letter values in the central circle, and 6 in the right hand circle.

Start at the top left of the diagram, and work down the left hand column, then along one space to the right and up the next column, in a snakes and ladders pattern, write the following repeated sequence of letters: A C P R F D U