1. **State the problem:** Simplify the expression $x + x$. 2. **Formula and rules:** When adding like terms, you add their coefficients. Here, both terms are $x$, which means the coefficient of $x$ is 1 for each term. 3. **Intermediate work:** $$x + x = 1x + 1x = (1 + 1)x = 2x$$ 4. **Explanation:** Since both terms are the same variable $x$, you add their coefficients (1 + 1) to get 2, then multiply by $x$. 5. **Final answer:** $$2x$$