Answer:
17
Explanation:
We are given the side lengths:
2
We check the triangle's inequalities if we add the third side of 20 cm:
3
Since one of the inequalities is not verified, the three given side lengths cannot form a triangle.
(Because the sum of two sides is equal to the third, we can say the triangle is degenerated to a segment.)
4
We check the triangle's inequalities if we add the third side of 15 cm:
5
Since all the three inequalities are verified, 15 can be the value of the third side.
RESULT - this one is 15 but the questions is move the 2 and it will give you 17
15 cm