Alphabet Test — “In the English alphabet, find the position of S from the right.” (Use 26-letter English alphabet, A=1 from the left.)

Introduction / Context:
Alphabet-position problems require converting between “from the left” and “from the right” indices in the 26-letter English alphabet. The letter S must be located from the right-hand side. Mastering the conversion formula avoids manual counting errors and speeds up solving.

Given Data / Assumptions:

• English alphabet length = 26.
• From the left: A=1, B=2, …, Z=26.
• We need the position of S when counting from the right (Z-side).

Concept / Approach:
The conversion formula between left-index L and right-index R in a 26-letter alphabet is:

because R + L = 27 for any letter (e.g., A is 1st from left and 26th from right → 1 + 26 = 27). First, find L(S), then compute R.

Step-by-Step Solution:

Verification / Alternative check:
Manual count from the right: Z(1), Y(2), X(3), W(4), V(5), U(6), T(7), S(8) — matches the calculation.

Why Other Options Are Wrong:
Numbers other than 8 fail the identity R + L = 27 with L=19.

Common Pitfalls:
Forgetting the 26-letter basis or miscounting by one. Always apply R = 27 - L to avoid mistakes.

Final Answer:
8