2, 4, 7, 12, 19, 30, ?

Differences: 2, 3, 5, 7, 11 — the prime numbers.
The next prime is 13, so the answer is 30 + 13 = 43.
Note: a difference sequence that starts 2, 3, 5, 7 is nearly always primes, not a "+1, +2, +2" pattern — check the next term before committing.

B3E, C5G, E7K, G11M, ?

Three tracks, and all three turn out to be primes:
First letters: B(2), C(3), E(5), G(7) → next is 11 = K.
Numbers: 3, 5, 7, 11 → next is 13.
Last letters: E(5), G(7), K(11), M(13) → next is 17 = Q.
Answer: K13Q.

B19N, E14P, ______, K7T, N5V

First letters: B(2), E(5), ?, K(11), N(14) — increasing by 3, so the missing one is 8 = H.
Numbers: 19, 14, ?, 7, 5 — the differences are −5, −4, −3, −2, giving 19, 14, 10, 7, 5.
Last letters: N(14), P(16), ?, T(20), V(22) — increasing by 2, so 18 = R.
Answer: H10R.

Z, X, 22, 20, R, P, 14, 12, J, ______, ______

Convert the letters to positions and the whole thing becomes one sequence:
Z = 26, X = 24, then 22, 20, then R = 18, P = 16, then 14, 12, then J = 10…
It is simply decreasing by 2 throughout, written alternately as two letters then two numbers.
Continuing: 8 falls in a letter slot → H; then 6 falls in a number slot → 6.
Answer: H, 6.
Note: the trap is answering "8, 6" or "H, F" — both appear in the options. The positions alternate in pairs, so you must track which form the next slot takes.

1/2, 8/5, 27/10, 64/17, ______, 216/37

Split the fraction into two series.
Numerators: 1, 8, 27, 64, ?, 216 — the cubes 1³, 2³, 3³, 4³, so the missing one is 5³ = 125.
Denominators: 2, 5, 10, 17, ?, 37 — these are n² + 1, so the missing one is 5² + 1 = 26.
Answer: 125/26.
Method: never treat a fraction series as one sequence. Numerator and denominator are always independent.