Let f(x) = x + floor(x) for x >= 0.
(a) Find all x >= 0 such that f(x) = 1.
(b) Find all x >= 0 such that f(x) = 3.
(c) Find all x >= 0 such that f(x) = 5.
(d) Find the number of possible values of f(x) for 0 <= x <= 10.
