Two sides of a triangle have lengths 9 and 14 units. describe what you know about the length of the third side.

Since we do not know anything about angles, all we can do is to give the maximum and minimum lengths of the  third side using the triangle inequality, which is:
the sum of lengths of the two shorter sides of a triangle must be GREATER than the third side (say X)

If 9 and 14 are the shorter sides, then the sum of 9 and 14 must be greather than the third side, X.  => 9+14=23>X, or X<23. (1)

If 14 is the longest side, then 9+third side (X) must be greater than 14, or 9+X>14, or X>14-9=5, or X>5, or 5< X (2)

Combining conditions (1) and (2)
5 < X < 23
OR
X must be greater than 5 AND X must be less than 23
OR
X must be between 5 and 23.