It seems like you're trying to evaluate the function $f(4) = 2x - 3$, but the variable $x$ is not defined in the expression. Based on the notation, you may want to evaluate the function for $f(x)$. Here's a clearer version:

1. If the function is $f(x) = 2x - 3$, then we substitute $x = 4$ to find $f(4)$: $f(4) = 2(4) - 3 = 8 - 3 = 5$

   So, $f(4) = 5$.

Would you like more details on function evaluation or have any questions?

Here are five related questions to deepen your understanding:

1. What happens if you change the function to $f(x) = 2x^2 - 3$?
2. How would you solve for $x$ if (