Starting with the top two segments, the sum of the numerical values of letters in adjoining segments equals 20.

In each diagram, add the numerical value of the upper right and left letters to the lower right and left letters, to give the letters in the centre of the columns. Calculate the difference between these middle letters to give the value of the letter right at the centre.

Start at the top to the left hand triangle, and work across the whole diagram in horizontal lines from left to right, top to bottom. Letters are written in alphabetic sequence, skipping 3 letters each time.

Starting in the top left of the diagram, and working in columns, from top to bottom, letters follow the alphabetical sequence, advancing 2 letters, then 4, then 6, then 8 etc.

Starting on the top left of each outer square, and moving clockwise around the corners of the squares, letters advance through the alphabet in steps of 4 for the upper left square, 5 for the upper right, 6 for the lower right and 7 for the lower left. Additionally, the letters bounded by the central square take the inverse alphabetical value of the original letter.

In each triangle, start with the bottom left letter, and move clockwise around the other points. Letters advance through the alphabet in steps given by the numerical value of the letter at the centre of the triangle.

Start on the left and work to the right. There are two alternating sequences of letters - one starts with A and moves through the alphabet 5 letters at a time. The other starts on H and moves through the alphabet 3 letters at a time.

Start on the top left, and work through the diagram in columns, from left to right. The sum of the numerical values of the letters in each column starts at 20, then increases by 1 as you move one column to the right.

Starting at the top left of the diagram, and moving in a Z shape, letters advance through the alphabet in steps of 5.

Start with the top point of each star, and move clockwise around the other points. Letters advance through the alphabet in steps of 5 for the left hand star, 6 for the right hand star, and 7 for the central star.

Working in columns, add the numerical value of the top and middle letters together to give the numerical value of the lower letter.

Start with the letter in the top left, and move clockwise around the square. The numerical value of the letters follows the sequence of prime numbers, from 2 to 19.

Starting in the top left, and moving in rows, left to right, top to bottom, letters advance through the alphabet in steps of 6, 7 and 8.

In each shape, start at the bottom left and move up, then diagonally down to the right, and finally up the right hand column, in an N shape. Letters move through the alphabet in steps of 4, 5, 6, 7, 8, and 9.

Starting at the top left hand of every diagram, move around the outer circles in an anti-clockwise direction. Letters are written in alphabetic sequence, in steps given by the numerical value of the central letter.

Start on the left of the middle row of letters, and move to the right, across all four diagrams. Letters advance through the alphabet in steps of 2, 3, 4... etc. In each separate diagram, letters also follow a sequence, moving from top to bottom, through the centre, with the value of the letters increasing by 2 each time for the left hand diagram, then 3, then 4, then 5 for the right hand diagram.

Start at the top, and work left to right in rows, top to bottom. Letters advance through the alphabet in steps of 10, 11, 12, 13 etc.

Start with A on the left hand side, and move in a clockwise spiral around the diagram. Letters advance through the alphabet in steps of 6.

Start on the top left of the left hand diagram, and move in horizontal lines, from left to right, top to bottom, across all 4 diagrams as a whole. Letters advance through the alphabet in steps of 7, then back 2, repeating this sequence all the way around.

Starting with the G and moving clockwise, letters advance through the alphabet in steps of 3 letters, then 4, then 5 etc.

Start in the bottom left hand corner of the diagram and, moving around the whole diagram, work in a clockwise direction, around the outer squares. Letters are written in alphabetical order, in steps of 7 letters at a time. For the single square still remaining in each group of 4, add the numerical values of the other 3 letters in the square together to give a 2 digit number, and add these separate digits together, and put the letter with this numerical value in the central square.

Start with the outer top left segment, and move around the circle clockwise, then move in to the middle segments and move anticlockwise. Following this path, letters advance through the alphabet in steps of 7 letters at a time.

Start with the top row, second square from the right, and move down and to the right in diagonal lines, advancing across the diagram to the left. Letters are written in alphabetical order, in steps of 5 at a time.

Start at the top left and move down the left hand column, then move one place to the right and up the next column etc. in a snakes and ladders pattern. Letters are written in alternate spaces, in steps of 7 letters at a time.

Starting on the left and moving right, letters are written in alphabetical order, using every other letter written with only straight lines.

The sum of the numerical values of letters in opposite segments of the circle is always 22.

In each grid, start in the top left and move down, then right one space and up etc. in a snakes and ladders pattern. Letters advance through the alphabet in steps of 5 for the top left grid, 6 for the top right, 7 for the bottom left and 8 for the bottom right.

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.

Starting at the left and moving right, the sum of the numerical values of the letters in each square follows the sequence 20, 22, 24 etc.

Start with the top left square, and move clockwise around the others. The sum of the numerical values of the letters in each square equals 20 for the top left, 25 for the top right, 30 for the bottom right and 35 for the bottom left.