Look at this series: XXIV, XX, __, XII, VIII, ... What number should fill the blank?
This is a simple subtraction series; each number is 4 less than the previous number.
SCD, TEF, UGH, ____, WKL
There are two alphabetical series here. The first series is with the first letters only: STUVW. The second series involves the remaining letters: CD, EF, GH, IJ, KL.
B2CD, _____, BCD4, B5CD, BC6D
Because the letters are the same, concentrate on the number series, which is a simple 2, 3, 4, 5, 6 series, and follows each letter in order.
FAG, GAF, HAI, IAH, ____
The middle letters are static, so concentrate on the first and third letters. The series involves an alphabetical order with a reversal of the letters. The first letters are in alphabetical order: F, G, H, I , J. The second and fourth segments are reversals of the first and third segments. The missing segment begins with a new letter.
ELFA, GLHA, ILJA, _____, MLNA
The second and forth letters in the series, L and A, are static. The first and third letters consist of an alphabetical order beginning with the letter E.