Here's a suggestion:
Treat the acetate ion (the #C_2H_3O_2 in the formulas) as a single unit, because it does not change in the process. This will greatly simplify the task, as your equation will now look like this:
where I substitute
Place a "1" in front of
Place a "3" in front of
Finally, you have a total of three oxygen atoms and six hydrogen atoms on the left side - just enough for three water molecules on the right.