Puzzle 1: Which number replaces the question mark?
Answer: 24
Explanation: Working clockwise around the diagram, add the first two numbers together and subtract 3 to give the next number along.
Puzzle 2: Which number replaces the question mark?
Answer: 24
Explanation: In each circle, the number in the lower segment equals twice the difference between the numbers in the left and right hand segments.
Puzzle 3: Which number replaces the question mark?
Answer: 1
Explanation: Working through the diagram in rows, the central value equals the sum of the other numbers in the row.
Puzzle 4: Which number replaces the question mark?
Answer: 8
Explanation: Multiply the 2 numbers in the outer segments together and add 1 to give the value in the inner segment opposite.
Puzzle 5: Which number replaces the question mark?
Answer: 3
Explanation: Split each grid into 2 halves, vertically, leaving 2 columns, each 2 squares wide. Start with the top left pair and move down, then to the top right pair, and down again. Reading each pair of digits as 2 digit values, the 2 digit values increase by 11, 12, 13, 14 and 15.