To solve the equation $-x = 4$, you can isolate $x$ by multiplying both sides by $-1$:

$x = -4$

So, the solution is $x = -4$.

Do you want details on how to solve similar equations or have any questions? Here are some related questions:

1. What is the significance of the negative sign in equations?
2. How do you check if your solution is correct?
3. Can you provide more examples of solving linear equations?
4. What happens if you have multiple variables in an equation?
5. How do you graph the solution of this equation on a number line?

Tip: Always isolate the variable by performing the same operation on both sides of the equation.