3 12 30 66 138 282 7 (a) (b) (c) (d) (e) Which of the following numbers will come in place of (b)?

As per the details in the question the series is in the form of
First series :-
First term = 3
Second term = First term × 2 + 6
⇒ Second term = 3 × 2 + 6 = 12
Third term = Second term × 2 + 6
⇒ Third term = 12 × 2 + 6 = 30
similarly , we can find the all others terms .
Second series :-
First term = 7
Second term = First term × 2 + 6
⇒ Second term = 7 × 2 + 6 = 20
Third term = Second term × 2 + 6
⇒ Third term = 20 × 2 + 6 = 46
Hence , the place value of ( b ) is 46 .