Select the option that is related to the fourth term in the same way as the first term is related to the second term and the fifth term us related to the sixth term.

16 : 96 :: ? : 161 :: 18 : 120

21

16 : 96 :: ? : 161 :: 18 : 120

The  logic followed here is :

{16 × ( 16 + 2 )} ÷ 3

= (16 × 18)  ÷ 3

= 96

AND

18 : 120

{18 × ( 18 + 2 )} ÷ 3

= (18 × 20)  ÷ 3

= 360

= 120

SIMILARLY

? : 161

{X × ( X + 2 )} ÷ 3 = 161

 X² +  2X = 483

 X² + 23X - 21X - 483 = 0

(X + 23) (X - 21) = 0

HERE X = - 23 AND X = 21