Correct Answer: (a) (11, 21, 40)
Solution:Logic :- (First number) Γ 2 - 1 = (Second number),
(Second number) Γ 2 - 2 = (Third number)
(19, 37, 72) β (19) Γ 2 - 1 = 37,
(37) Γ 2 - 2 = 72
(15, 29, 56) β (15) Γ 2 - 1 = 29,
(29) Γ 2 - 2 = 56
Similarly, (11, 21, 40) β (11) Γ 2 - 1 = 21,
(21) Γ 2 - 2 = 40