When we write an inequality in the form:
[tex]1We are indicating the both are true: x is greater than 1 and x is less than 5. This means that x is between 1 and 5 (not including neither ends).
In a number line, we can draw it, mark the endpoints (1 and 5) and then we highlight the parts at which the x is, which is in the middle:
Notice that we marked the endpoints as empty dots, which indicates that the endpoints are not included in the interval.