16) \( (x)\left(x-\frac{y}{5}\right) ; \) use \( x=4 \), and \( y=5 \)

First, let's substitute the given values of \( x \) and \( y \) into the expression. Plugging in \( x = 4 \) and \( y = 5 \) into \( (x)\left(x - \frac{y}{5}\right) \) gives us: \[ (4)\left(4 - \frac{5}{5}\right) = (4)\left(4 - 1\right) = (4)(3) = 12. \] So the result of the expression is 12! Now, if you're looking to dive deeper into the concept of algebraic expressions like this one, consider how these basic forms can be expanded into more complex equations. Practicing with different values and interpretations can help to solidify your understanding of how variables interact. Don’t forget to explore how this forms the basis for solving quadratic equations and more in advanced math! When grappling with expressions, a common pitfall is forgetting to handle order of operations (PEMDAS/BODMAS). Always simplify inside the parentheses first before multiplying, or you might find numbers running away from you! Another tip is to double-check your substitutions to make sure everything lines up correctly; small mistakes can lead to totally different answers!