In the series 9 N ! 3 P Q 6 E 1 V # 8 L 2 Z 7 A (17 elements), how many letters have a digit standing immediately before them and a digit standing immediately after them?

Test each letter. N has 9 before it but the symbol ! after it. P has 3 before it but Q after it. Q has P before it. E sits between 6 and 1 — counts. V has 1 before it but # after it. L sits between 8 and 2 — counts. Z sits between 2 and 7 — counts. A has 7 before it but nothing after it. So E, L and Z qualify, giving 3. Answering 4 or 5 comes of admitting letters such as P, V or A that meet the rule on one side only, and 2 of overlooking one of the three.