What letters will fill the blank?

Z, X, V, T, R, __,__

A series is given with one term missing. Select the correct alternative from the given ones that will complete the series.
250, 275, 301, ?

A series is given with one term missing. Choose the correct alternative from the given ones that will complete the series.
14, 22, 33, 47, 64, ?

A series is given, with one number missing. Choose the correct alternative from the given ones that will complete the series.
-4, ? , 1, 3.5, 6, 8.5

In the following question, select the missing number from the given series.

59, 68, 78, 89, 101, ?

Which of the following terms follows the trend of the given list?

XYXYXYxY, XYXYXyXY, XYXYxYXY, XYXyXYXY, XYxYXYXY,  _______________.

In the following question, select the missing number from the given series.

2187, 729, 243, 81, 27, ?

In the following question, select the missing number from the given series.

10, 12, 14, 16, 18, ?

In the following question, select the missing number from the given series.

11, 13, 16, 18, 21, ?