The expression you’ve given, $x - 13$, represents a linear expression in one variable, $x$, with 13 subtracted from it. Without additional context (such as an equation to solve or more operations), it remains in its simplified form.

Would you like me to assist with an equation, or do you want further steps involving this expression?

Here are some related questions:

1. How would you solve $x - 13 = 0$?
2. What happens if you add 13 to both sides of $x - 13 = 10$?
3. How would you graph $y = x - 13$ on a coordinate plane?
4. What if $x = 5$, what does $x - 13$ evaluate to?
5. How do you solve $x - 13 = 5x$?

Tip: Always isolate the variable when solving equations to simplify the process.