If in a certain language, COUNSEL is coded as BITIRAK, how is GUIDANCE written…

Concept: In this style of position-based coding-decoding puzzle, every letter of the word shifts backward along the alphabet by an amount that depends only on whether its position, counted from the left starting at 1, is odd or even. Odd positions all shift back by the same fixed step; even positions shift back by a steadily decreasing sequence of steps.

Confirming the rule on COUNSEL -> BITIRAK: the 1st, 3rd, 5th and 7th letters (C, U, S, L) each shift back by 1, while the 2nd, 4th and 6th letters (O, N, E) shift back by 6, 5 and 4 respectively.

GUIDANCE has 8 letters, so the even-position sequence continues one step further (6, 5, 4, 3) while every odd position again shifts back by 1:

1. G (1st, odd) shifts back 1 -> F

2. U (2nd, even) shifts back 6 -> O

3. I (3rd, odd) shifts back 1 -> H

4. D (4th, even) shifts back 5 -> Y (past A, wrapping to the end of the alphabet)

5. A (5th, odd) shifts back 1 -> Z (wrapping to the end of the alphabet)

6. N (6th, even) shifts back 4 -> J

7. C (7th, odd) shifts back 1 -> B

8. E (8th, even) shifts back 3 -> B

Reading the shifted letters in order gives the code FOHYZJBB.

Cross-check with modular alphabet arithmetic (A=1 ... Z=26, wrapping after Z back to A): D=4, so 4-5=-1, which wraps to 25=Y; A=1, so 1-1=0, which wraps to 26=Z. Both match the wrap-around letters obtained above, confirming the code FOHYZJBB.