Given 5, 7, 9

Yes, these numbers can be the lengths of the sides of a triangle because the sum of any two sides of a triangle is always greater than the third side.

Here, 5 + 7 > 9, 5 + 9 > 7, 9 + 7 > 5

Let the length of the third side be x cm.

We know that the sum of any two sides of a triangle is greater than the third.

∴ (6 + 8) > x ⇒ x < 14

Also, we know that the difference between any two sides of a triangle is less than the third side.

∴ (8 – 6) < x ⇒ x > 2

Thus, 2 < x < 14

Hence, the length of the third side must be larger than 2 cm and smaller than 14 cm.