1. **State the problem:** Simplify the expression $X9 + 1$. 2. **Identify the expression:** The expression appears to be $X9 + 1$. Assuming $X9$ means $9X$ (9 times $X$), the expression is $9X + 1$. 3. **Simplify the expression:** Since $9X + 1$ is already simplified (no like terms to combine), the expression remains $9X + 1$. 4. **Final answer:** $$9X + 1$$ This is the simplified form of the expression.