Find the missing number from the given responses.

4    8     2

3    2     2 

5     8     ?

60 128 68

Find the missing number in the following?

5,22,68,153,287, .........., ?

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?