Given: (n + 3)! = 56 [(n + 1)!]

To Find : n

⇒ (n + 3) × (n + 2) × (n + 1)! = 56 [(n + 1)!]

⇒ (n + 3) × (n + 2) = 56

⇒ (n + 3) × (n + 2) = 8 × 7

⇒n + 3 = 8

n = 5

Hence, n = 5