1. **State the problem:** Simplify the expression $x + x$. 2. **Recall the rule:** When adding like terms, you add their coefficients. 3. **Apply the rule:** Both terms are $x$, so their coefficients are 1 and 1. 4. **Add the coefficients:** $1 + 1 = 2$. 5. **Write the simplified expression:** $2x$. **Final answer:** $2x$