An inequality is a statement that shows relation between two values, when the two values are not equal.
The inequality is opposite than equality.
So, the interval (5,100] means that it contains all number from number 5 (not and 5) till 100, including 100. We can see this from the bracket's type.
For a value x in this interval we can write the inequality:
5<x<=100
x is bigger than 5 , and smaller or equal 100