In a triangle, the sum of the lengths of any two sides must be greater than the length of the third side. Using this fact, we can write:
5 + 12 > n
and
5 + n > 12
and
12 + n > 5
Simplifying these inequalities, we get:
17 > n
and
n > -7
and
n > -5
Therefore, the interval of values that n may have is -7 < n < 17.