Find $x$ so that the arithmetic mean of $x, 3x, 1000$, and $3000$ is $2018$.
1. Start with the given arithmetic mean equation:
   \[
   \frac{x + 3x + 1000 + 3000}{4} = 2018
   \]

2. Combine like terms in the numerator:
   \[
   \frac{4x + 4000}{4} = 2018
   \]

3. Simplify the left-hand side by dividing each term in the numerator by 4:
   \[
   x + 1000 = 2018
   \]

4. Solve for \( x \) by isolating \( x \):
   \[
   x = 2018 - 1000
   \]
   \[
   x = 1018
   \]

The final answer is \( \boxed{1018} \)