Find the missing number 

3,7,9,13,15,19,-------,25,......

Find the missing numbers in this series:

2,6,18,54,-----------------486,1458

 What is the missing number ‘X’ of the series 7, X, 21, 31, 43?

32. Consider the following matrix:
3    8    10    2    ?    1
6    56    90    2    20    0
What is the missing number at ‘?’ in the matrix?

Find the missing number : 3, 5, 7, 11, 13, .........