8 B R 4 % W 6 F 2 D @ 9 J 7 K * 3 5 T — in this series, how many elements lie between the fourth element from the left end and the fifth element from the right end?

The fourth from the left is the 4 at place 4. The fifth from the right stands at place 19 − 5 + 1 = 15, the letter K. The elements strictly between them run from place 5 to place 14, which is 14 − 5 + 1 = 10 elements (% W 6 F 2 D @ 9 J 7). Answering 11 or 12 comes of counting one or both of the two named elements as lying 'between' them, which the word does not allow; 9 comes of dropping one from the run.