Answer:
is increasing.
Step-by-step explanation:
I'll try to give you an intuition - although informal, of course. If
is a decreasing function, then
means to read the graph of
"backwards", and thus making it increasing. At that point,
is a composition of two increasing function, and is thus increasing.
Now, for a formal answer, let's simply pick two inputs
(we will assume that the range of
is part of the domain of
, otherwise you couldn't compute
)
Since
is decreasing, we have

But we want to compute
, so we have

Since
is increasing, we have

and thus

So, we've shown that, given two inputs
, the images are in the same order: 
This, by definition, means that
is an increasing function.