Concept: The question tests on the basics of Counting
Choose the number that has to come twice. This can be done in nC1 = n ways.
Next choose the number that has to come once. This is done in (n-1) C1 = n - 1 ways
These 2 numbers can be arranged in 3! /2! = 3 ways
Total number of ways = n * (n - 1) * 3 = 3n (n - 1) ways
This value has to be between 120 and 130, let us say m.
From this we understand that m has to be divisible by 3 and m/3 has to be even as n(n - 1) is the product of 2 consecutive numbers which will always be even.
Therefore m = 126 and m/3 = 42
n(n - 1) = 7 * 6. Therefore n = 7