Fill in the blank space for the given series with the correct alternative.
$66, 36, 18, (...)$

Study carefully the following arrangement of letters, digits and symbols to answer these

questions.

$M, 7 ,\&, 8, L ,P ,@ ,Q ,N ,\beta ,T ,Y ,3 ,2 ,= ,E ,\$ ,4 ,9 ,\#, G ,H ,5$

How many such symbols are there in the arrangement each of which is immediately preceded by a number?

Study the following arrangement carefully and answer the questions given below:

$7, R,E,T ,4 ,A ,9 ,\% ,D,F, 1, U, \# ,B ,@ ,8 ,H,I ,$©$, W,M, \star, 3,2 ,V ,\$ ,5 ,N,P,6, Q$

How many such consonants are there in the above arrangement, each of which is immediately preceded by a consonant and immediately followed by a number?

Find the missing letters for the given series from the given alternatives.
$b....b...bb....,.....bbb.....bb....b$

Fill in the blank space for the given series with the correct alternative.
$2, 5, 9, (\ldots), 20, 27$

What should come next in the following letter series?
$H, G, F, E, D, C, B, A, G, F, E, D, C, B, A, F, E, D, C, B, A, ?$