Answer
All of the functions from the family are parallel to each other with the slope of $-1$.
On the figure are the members of this family for $c=-2$(blue), $c=0$(orange) and $c=1$(green)
Work Step by Step
The general equation of linear function is
$$f(x)=kx+c$$
where $k$ is the slope.
Any given function from this family can be rewritten as
$$f(x)=-x+c$$
We see that all of these functions are parallel to each other with the slope of $-1$.
On the figure are the members of this family for $c=-2$(blue), $c=0$(orange) and $c=1$(green)
