Answer:
The sum of two side lengths of a triangle must be greater than the length of the third.
So, if two side lengths are 3 and 7, the length of the third side must be less than 10 units.
However, it cannot be shorter than 4 units, as 3 + 4 = 7.
So your answer is: The third side of this triangle must not be shorter than 4 or longer than 10
Let me know if this helps!