Look at this series: XXIV, XX, __, XII, VIII, ... What number should fill the blank?

Look at this series: XXIV, XX, __, XII, VIII, ... What number should f

1.	Look at this series: XXIV, XX, __, XII, VIII, ... What number should fill the blank?
Answer» This is a simple subtraction series; each number is 4 less than the previous number.