In each diagram, add the numerical values of the top 2 letters together, divide this by 2 and subtract 2 to give the numerical value of the lower letter.

Start on 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.

Split the diagram in half, horizontally and vertically, into quarters. Start in the top left cell of each quarter, and move around it in a clockwise spiral towards the centre. Letters are written in alternate segments, moving forward 7 letters at a time for the top left quarter, 6 letters for the top right, 5 letters for the lower right, and 4 letters for the lower left.

The sum of the numerical values of the letters in each column of the diagram equals 29.

The sum of the numerical values of the letters in opposite segments of the circle equals 26.

Start with the A in the top left hand segment, and move in straight vertical lines, from top to bottom, left to right. Letters follow the alphabetic sequence, skipping 1 letter, then 2, then 3 etc.

As you move down, add the number of straight lines in the first letter to the numerical value of that letter to give the next one down.

Start at the top left, and move around the diagram in a Z shape. The numerical value of the letters increases alternately by 6, then 3.

Convert each letter to its numerical value, and split the diagram into rows, reading each row as a 2 or 3 digit value. The value represented by the middle line of the diagram equals the sum of the upper value and lower value.

Working through the diagram in columns, from top to bottom, letters move through the alphabet in steps of 5 for the left hand column, 7 for the next one, then 9, then 11.

Start with the letter J in the top left square, and move clockwise around the other squares. Letters follow the alphabetic sequence, skipping 4 letters at a time. Start with the X in the inner square in the top left, and move clockwise. These inner letters also follow the alphabetic sequence, skipping 5 letters at a time.

Start on the top left of the diagram, and move from left to right, top row to bottom row. Letters advance through the alphabet in steps of 6, 7 then 8, before repeating this pattern.

Starting on the top left, and moving around the whole diagram in an anti- clockwise direction, outside then inside, letters advance through the alphabet 5 letters at a time.

Start with the H in the top left segment, and move clockwise around the shape, alternating between outer segment then inner segment. Letters advance through the alphabet 6 letters at a time.

Start at the top of the triangle and move anti-clockwise around it. Letters move through the alphabet in steps of 3, 4, 5, 6 etc.

Start with the A in the bottom left corner, and move in a clockwise spiral around the diagram towards the centre. Letters are written in alphabetic order, in steps of 6 letters at a time.

Start with the top left grid and move around the others in a clockwise spiral towards the centre. Letters follow alphabetic sequences, skipping 1, 2, 3 and 4 letters at a time, with their relative positions in each grid rotating 1/4 turn clockwise each time.

Starting with H and moving anti-clockwise, letters advance through the alphabet in steps of 10, then 8, then 6 etc.

In each row, add together the numerical values of the pairs of letters to the left and right, then calculate their difference, putting the letter with this numerical value in the center space.

Start on the left hand side, and move clockwise around the diagram. Letters advance through the alphabet 9 letters at a time.

Start with the top segment of the top left square, and move directly downwards. Each group of 4 letters follows the alphabetic sequence, in steps of 5 letters at a time. Taking other straight lines vertically and horizontally through the diagram, letters follow the same pattern.

Working from left to right, replace each letter with its numerical value and read each pair of numbers as a 2 digit number. Numbers follow the sequence of multiples of 9, from 27 to 72.

Start with the outer segment in the top left, and move anti-clockwise. Letters advance through the alphabet in steps of 6, then 7, then 8. Continue around the outer segments of the diagram, then move in an anti-clockwise direction around the inner segments.

Starting with the top left letter, and moving clockwise around the others, letters advance through the alphabet in steps given by the numerical value of the central letter (6).

Working in rows, from top to bottom, the sum of the numerical values of the letters follows the sequence 16, 18, 20, 22, 24.

Start at the top, and work through the triangle in horizontal rows, from top to bottom, left to right. Letters move through the alphabet 5 letters at a time.

In each group of 3 boxes, calculate the difference in numerical values between the top two letters, and add 1 to give the value of the letter in the lower box.

Start with the letters in the top left circle, and move around the other circles in a clockwise direction. Letters advance through the alphabet 6 letters at a time, with the relative positions of each letter moving one place clockwise each time.

In each star, start with the letter in the lower left hand point, and move around the other points in a clockwise direction. Letters advance through the alphabet in steps of 6 for the left hand star, 7 for the right hand star and 8 for the one in the centre.

Working from left to right, letters move through the alphabet in steps of 2, then 3, then 2 etc.