Taking the positions of letters A = 1, B = 2 and so on. Multiplying the combination by 2, 12 * 2 = 24 = BD Similarly, AC = 13 Multiplying it by 2, we get 13 * 2 = 26 = BF.

Considering the positions of letters, we get A = 1 : Z = 26 Again in the next case, B = 2 : Y = 25, which again sums to 27. Similarly, K = 11, so we need 16, which is P. L = 12, so we need 15, which is O. M = 13, so we need 14, which is N. N = 14, so we need 13, which is M. So, the code should be PONM.

GREEN = RED, RED = BLUE and BLUE = BLACK. So, the code for GREEN is BLUE will be RED is BLACK.

As given in the question, K = 121. The positional value of K is 11. Squaring, it becomes 121. So, the square of the positional value of Y will be 625(25²).

As from the question, the letters of the word CASE are shuffled as first two letters become the last two letters and last two letters become the first two letters. So, TAPE will be PETA.

Square root of 16 = 4. So, D is the code for P. Similarly, Y = 25. Square root of 25 = 5. So, E will be the code for Y.

A = 2, B = 4 So, the positional values of the letters are getting doubled. In the same way, sum of values of letters in the word WORD = W(23) + O(15) + R(18) + D(4) = 60 * 2 = 120.

The consonants and vowels are place together. Vowels = A, E, E, U. Consonants = C, D, T. So, AEEUCDT is the answer. Also, vowels come first.

Here, the letters of the word are 5 letters ahead of the preceding figure. F is 5 letters ahead of A. Similarly, K is 5 places ahead of F. Same pattern is followed here.

Adding the place values of A, C and E, we get 1 + 3 + 5 = 9, the place value of I. So, it is represented by I. Similarly, G = 7, H = 8 and I = 9. 7 + 8 + 9 = 24, which is represented by X. It is the correct answer.

The letters of the word increase by 2 places. Adding 2 in it will give 3, which is the value of C.

A letter is represented by two letters, first is one place backward and other one place forward. B is represented as A, the backward letter and C, one place forward letter.

D is represented by B. The place value of D is 4, which is halved and the result is 2, the place value of B. Similarly, X = 24. Dividing it by 2, we get 12. It is the place value of L. So, this is the correct answer.

A = 1 * 2 + 1 = 3, which is the place value of C. Similarly, B = 2 * 3 + 2 = 8, which means H. Similarly, C = 3 * 4 + 3 = 15 = O. Similarly, D = 4 * 5 + 4 = 24 = X. So, this is the answer.

The place values of H and B are 8 and 2 are multiplied to get 16, which is the place value of P. Similarly, C and F (place values 3 and 6), when multiplied, give 18. 18 is the place value of R. So, this is the correct answer.