If a triangle has the lengths of 3 sides a, b, and c
Then the length of any side must lie between the different and the sum of the other two sides
a - b < c < a + b
a - c < b < a + c
b - c < a < b + c
Let us use this rule to solve the question
Since the triangle has 2 sides 5 and 8
Since 8 - 5 = 3, and 8 + 5 = 13, then
The third side must lie between 3 and 13
3 < 3rd side < 13