**Puzzle 1:** Which letter replaces the question mark?**Answer:** F

**Explanation:** Working in rows, from top to bottom, the sum of the numerical values of the letters in each row starts at 12, and increases by 2 as you go down each row.

**Puzzle 2:** Which letter replaces the question mark?**Answer:** G

**Explanation:** The numerical values of the letters in opposite segments of the circle add up to 16 each time.

**Puzzle 3:** Which letter replaces the question mark?**Answer:** H

**Explanation:** Working from top to bottom, letters are written in pairs. Take the 2 digit numerical value of the first letter and add the 2 digits together. Write the letter with this numerical value in the next space down. Continue in this way down the line.

**Puzzle 4:** Which letter replaces the question mark?**Answer:** N

**Explanation:** Moving from left to right, top to bottom letters follow alphabetical order, skipping any letters written with curved lines.

**Puzzle 5:** Which letter replaces the question mark?**Answer:** S

**Explanation:** Working from top to bottom, the numerical values of the letters follow the sequence of Prime Numbers, adding 1, then 2, then 3 etc.