---

Answer: M

Explanation: 

In each column, add up each number and put the letter with this sum in the bottom circle.

---

Answer: 6

Explanation: 

In each row of the diagram, the numerical value of the middle letter equals the sum of the left and right hand numbers, subtracting 3.

---

Answer: B Grid

Explanation: 

Working in rows, left to right, top row then bottom, one black circle is added each time, with the positions of the circles moving (1/4) turn clockwise each time.

---

Answer: F

Explanation: 

In each diagram, convert each letter to its numerical value, and read the top and bottom pairs of letters as complete 2 digit values. Multiply these values together to give the 3 digit result written in the centre spaces.

---

Answer: Z

Explanation: 

In each row, multiply the numerical values of the left and right hand letters, putting the result in the centre.