Question

For how many positive integers n is it possible to have a triangle with side lengths five, 12, and n

Answer 1

Explanation:

you know, a single side cannot be longer than the other 2 sides combined.

otherwise, the triangle cannot "close".

so, it starts with 12 cannot be longer than 5 + n.

therefore, n must be at least 7.

and n cannot be longer than 5+12 = 17

7 and 17 I would normally rule out a well, because in these cases the triangle would just be a flat line, when the 3rd side is as long as the other 2 combined.

so, in reality for a real, visible triangle, the range of valid values is 8 .. 16.

that is 9 positive integer values.