Answer:
The third side must be greater than 9 and less than 17.
9 < x < 17
Explanation:
The Triangle Inequality Theorem says that if you know two sides of a triangle, and you subtract them and you add them (get two separate numbers), the third side will be in between those numbers. So if you have 4 and 13 as the two sides.
13 - 4 is 9. The third side has to be bigger than 9.
Then, 13 + 4 is 17. The third side has to be smaller than 17.
9 < x < 17