1. **State the problem:** Simplify the expression $8x + 9 - 5x$. 2. **Recall the rule:** Combine like terms, which means adding or subtracting coefficients of the same variable. 3. **Combine like terms:** $$8x - 5x = (8 - 5)x = 3x$$ 4. **Rewrite the expression:** $$3x + 9$$ 5. **Final answer:** The simplified expression is $3x + 9$.