As can be seen in the diagram:
only the values to the left of #3# are included in
#color(white)("XXX")x < 3 # AND #x < 5#
In interval notation
#color(white)("XXX")in# means "in" or that #x# is included in the interval that follows;
#color(white)("XXX")#rounded brackets mean that the value beside the bracket is not included in the set (but everything up to that value) is;
#color(white)("XXX")#square brackets mean that the value beside the bracket is included in the set (as well as everything up to that value.
Note that the "infinite" values, #-oo# and #+oo# are always not included (always written with round brackets).
Some examples:
#color(white)("XXX")x in [-2,+7)# would mean #-2 <= x < 7#
#color(white)("XXX")x in (4,+oo)# would mean #4 < x# (with no upper limit)
For the given case
#color(white)("XXX")x < 3# implies #x < 5#
#color(white)("XXX")#so if both are included in th4e restrictions (AND) then only the #x < 3# is required
so we would write the interval as:
#color(white)("XXX")x in (-oo,3)#
