Solution:The pattern followed here is :(1st number + 2nd number) × 5 = 3rd number
(5, 11, 80) → (5 + 11) × 5 ⇒ (16 × 5) = 80
(6, 12, 90) → (6 + 12) × 5 ⇒ (18 × 5) = 90
Similarly,
(7, 17, 120) → (7 + 17) × 5 ⇒ (24 × 5) = 120
Hence, (7, 17, 120) is the correct answer.