Select the number from among the given option that can replace the question mark (?) in the following series.

6, 31, 126, 381, 766, ?

2, 5, 11, 23, ?

19 : 109 ∷ 21 : ?

Select the combination of numbers that when placed sequentially in the blanks of the given series will complete the series.

Select the option that is related to the third number in the same way as the second number is related to the first number.

15 : 5 :: 26 : (?)

UDGO : FWTL : : MXRC : ?

In the following expression find the missing term:  

Find the missing number. 

Select the number from among the given options that can replace the question mark (?) in the following table.