Algorithm $X$ proceeds by recursively solving $5$ subproblems of one-half the size, then combining the solutions in $O(n\log n)$ time.
Algorithm $Y$ makes $9$ recursively calls on subproblems with one-third the size, then combining the solutions in $O(n^2)$ time.
What do the last parts of these sentences mean? "Combining the solutions in $O(...)$ time? Can we represent $X$ and $Y$ by:
$$X(n) = 5X(n/2)+n\log n$$
$$Y(n)=9Y(n/3)+n^2$$
Or does it mean something different?