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:
1/4 times 4 is 1 hour so
3 1/6 times 4 is 12 2/3
A decade is 10 years which means 1/5 is 2 years. thus making 2/5 4 years.