v is 4 more tha x
v=4+x
sum is no more than 14
v+x≤14
sub 4+x for v
4+x+x≤14
4+2x≤14
minus 4 both sides
2x≤10
divide both sides by 2
x≤5
5+4=9
the neighboor's age is 5 years
and victoria is 9
Answer:
a) Suppose that F is ordered in ascending order: 
. Then, the complement of F can be written as
which is the union of a finite number of open intervals, then 
is an open set. Thus, F is a closed subset of the real numbers.
b) Take an arbitrary element of F, let us say 
. Now, choose a real number 
such that
there are not other element of F, because is less that the minimum distance between and its neighbors.
In case that 
we only consider 
, and if 
we only consider 
.
Then, all points of F are isolated.
Step-by-step explanation:
