Look at this series: V, VIII, XI, XIV, _____ XX. What number should fill the blank?

Look at this series: V, VIII, XI, XIV, _____ XX. What number should fill the blank?

Explanation

The series is formed by incrementing the Roman numerals by 3:

V (5) + 3 = VIII (8)

VIII (8) + 3 = XI (11)

XI (11) + 3 = XIV (14)

XIV (14) + 3 = XVII (17)

So, the next number in the series is XVII.