In each segment of the circle, multiply the outer 2 numbers together and subtract the sum of the outer 2 numbers in the opposite segment to give the value in the inner grey segment.

In each diagram, the sum of the three upper numbers equals the product of the two lower numbers. So, 4 * 6 = 13 + x + 6 x = 24 - 19 x = 5.

Moving left to right, the numbers represent multiples of 12, subtracting 1, for the first step, adding 2 for the second, subtracting 3 for the third, adding 4 for the next etc. etc. So, 12 * 7 + 6 = 90.

In each row, the sum of the digits is 10. So, 3 + 4 + x = 10. x = 10 - 7 = 3..

First Number = Square of 1 * 2 = 2. Second Number = Square of 2 * 2 = 2 *2 * 2 = 8. Third Number = Square of 3 * 2 = 9 * 2 = 18. Fourth Number = Square of 4 * 2 = 16 * 2 = 32. Fifth Number = Square of 5 * 2 = 25 * 2 = 50. So, Missing number = Square of 6 * 2 = 36 * 2 = 72.

Values in the lower left table equal the sums of the values in corresponding positions of the top two tables, and values in the lower right table equal the difference in values in corresponding positions of the top two tables. Missing Number = 1 - 0 = 1.

Reading each horizontal line as a 4 digit number, add together the top two rows to give the result in the third row, and subtract the second row number from the first to give the result in the fourth row.

Each number represents the numerical value of the vowels in the alphabet.

Add up the four outer numbers and place your answer in the centre square of the shape one place clockwise. So, 7 + x + 4 + 2 = 14. x = 1.

Split the grid in half vertically, to give two columns, 3 squares wide. Working from top to bottom, left then right, and reading each 3 square row as a whole 3 digit number, the columns follow the sequence of square numbers, from 10 to 21.So, last three digit number would be square of 21. 21 * 21 = 441. Missing Element = 1.

Working from the top row, add the values in adjacent boxes and put this sum in the box directly below, working towards the centre. Repeat this pattern starting at the bottom row as well. Thus, 4 + x = 5. x = 1.

Taking any series of 3 numbers in a straight line in the diagram, their total is always 19. So, 4 + 14 + x = 19. x = 1.

The diagram contains two diamonds of 3x3 circles, arranged side by side, with the central 4 circles overlapping. Starting in the central left circle of each diamond, the numbers from 1 to 9 are written in lines, moving up and to the right. In the circles where the diamonds overlap, the values are added together to give the ones shown on the final diagram.

Moving Left to Right: 8 + 4 = 12 12 + 3 = 15 15 + 2 = 17 Now repeat, 17 + 4 = 21 21 + 3 = 24 24 + 2 = 26. Again, 26 + 4 = 30 Missing Number = 30. 30 + 3 = 33 33 + 2 = 25

Working in rows, from top to bottom, the sum of the digits in each row increases by 2 each time, from 8 to 16. So, Sum of the bottom row = 16 8 + 4 + x = 16 x = 4

Numbers in the segments of the lower left circle equal the sum of the numbers in the upper left and central circles. Numbers in the segments of the lower right circle equal the sum of the numbers in corresponding segments of the upper right and central circles.

The numbers on the points of the lower triangle equal the sum of the numbers on corresponding points of the upper two triangles. So, Missing number = 6 + 4 = 10.

Logic: Central Number = Multiplication of lower numbers + upper number So, Missing Number = 5 * 8 + 3 = 43.

72 72 - 3 = 69 69 - 5 = 64 64 - 7 = 57 57 - 9 = 48. 48 - 11 = 37 So, Missing Element = 37.

Working in rows, the sum of numbers in each row follows the sequence 5, 10, 15, 20, 15, 10, 5. So, Sum of the middle = 20 1 + 3 + 7 + x + 1 + 4 + 2 = 20 x = 20 - 18 = 2. Missing element = 2.

Working from left to right, the sum of the two smaller numbers on each triangle equals the third number. And the bigger number is rotating clockwise. So, in third triangle, Missing Element, x + 6 = 15. x = 15 - 6 = 9.

Logic (Moving-Down): 7122 = 7 + 1 + 2 + 2 = 12. 6521 = 6 + 5 + 2 + 1 = 14. 8332 = 8 + 3 + 3 + 2 = 16. 4743 = 4 + 7 + 4 + 3 = 18. 9911 = 9 + 9 + 1 + 1 = 20. So, sum of the last oval box = 22. 387x = 3 + 8 + 7 + x = 22. x = 22 - 18 = 4. Missing Element = 4.

Logic: Element in Lower left segment = Sum of the upper segment element Element in Lower right Segment = Difference of the Upper segment element Missing Number = 5 - 4 = 1.

The number in the centre of each star equals the average of the surrounding 5 numbers. So, Central number of last figure = ( 7 + 7 + 2 + 2 + 12)/5. X * 5 = 30 X = 6.

In each diagram, the sum of the upper left and upper middle numbers is written in the centre box, and the sum of the upper right and upper middle numbers is written in the lower central box. So, Missing number = 4 + 3 = 7.

Looking at the diagram as two columns, numbers in the left hand column increase by 5, 6, 7 etc, and numbers in the right hand column increase by 6, 7, 8 etc. So, Missing Number = 15 + 8 = 23.

The number at the centre of each segment equals the sum of the numbers on the outside of the opposite segment. So, 3 + x = 9. x = 6 .

The numbers in the lower circles equal the numbers in corresponding segments in the upper circles multiplied by two, then subtract 3 for the left hand circle, 4 for the middle and 5 for the right hand circle.

Logic: Central Element = Sum of the left column element - sum of the right column element. Thus, x = 4 + 8 +2 - 5 + 1 + 3 x = 5. Missing Number = 5.