The process of killing pupa without changing the cocoon

Study the given pattern carefully and select the number that can replace the question mark (?) in it.

 First row: 84, 42, 49

C/JQ : B/GT : : Z/CX : ?

What will come in place of question mark [?] following the same pattern as given below?

Find the missing number.

20, 30, 42, 56, 72, ?

Find the missing number.

Select the missing number from the given responses:

Find the missing number. 

Select the related word/letters/number from the given alternatives.

LHX: OEA : : PFT : ?

Find the missing term in the following question:

Select the number that can replace the question mark (?) in the following series.