1. **State the problem:** Simplify the expression $x + x$. 2. **Formula and rules:** When adding like terms, you add their coefficients. The variable part remains the same. 3. **Intermediate work:** $x + x = 1x + 1x = (1 + 1)x = 2x$ 4. **Explanation:** Since both terms are $x$, you add the coefficients $1 + 1$ to get $2$, so the simplified expression is $2x$. **Final answer:** $2x$