Working in rows from top to bottom, the sum of the digits in each row increases by 2 each time, from 20 to 30.

Working in rows, the number in the central oval equals the sum of the left and right hand numb

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.

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.

In each diagram, the sum of the three upper numbers equals the product of the two lower numbers.