4) \( \frac{9 x^{5} y^{2}}{3 y} \)

To simplify \( \frac{9 x^{5} y^{2}}{3 y} \), you start by dividing the coefficients and then simplifying the variables. The coefficient \( \frac{9}{3} = 3 \). For the \( y \) terms, you have \( \frac{y^{2}}{y} = y^{1} = y \). Thus, the simplified expression is \( 3 x^{5} y \). In mathematical expressions, simplifying fractions is like tidying up your closet—it helps you see what you really have at a glance! Keeping your math neat allows for easier problem-solving in future calculations. Also, when working with fractions, remember to look out for common mistakes like forgetting to simplify fully or mishandling negative signs. Stay mindful of your math rules, and you’ll keep your expressions clearer and more manageable!