What letters will fill the blank?

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

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

3, 4, 6, 9, 13, ?

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

19, 26, 40, 61, ?, 124

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

46, 45, 43, 42, 40, 39, ?

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

9, 13, 22, 38, 63, ?

In the following series, one number is missing as shown by the question mark. Select the missing number from the given options.

8, 12, 16, 20, ?

Find the number which will complete the following series.

0, 1, 8, 27, ?

Find the missing number (?) in the series

1, 1, 4, 8, 9, ?, 16, 6,...

Find the first negative term of the below A.P.

129, 120, 111, 102, ...