1. **State the problem:** Simplify or analyze the expression $4x - 3y$. 2. **Understand the expression:** This is a linear expression with two variables $x$ and $y$. It cannot be simplified further without additional information or values for $x$ and $y$. 3. **No further simplification:** Since $4x$ and $-3y$ are unlike terms (different variables), they cannot be combined. 4. **Summary:** The expression $4x - 3y$ is already in its simplest form. Final answer: $4x - 3y$