1. **State the problem:** We need to express "two times a number plus nine" as an algebraic expression. 2. **Define the variable:** Let the number be represented by $x$. 3. **Write the expression:** "Two times a number" means $2 \times x$ or $2x$. 4. **Add nine:** Adding nine to this gives the expression $2x + 9$. 5. **Final expression:** Therefore, the algebraic expression for "two times a number plus nine" is: $$2x + 9$$ This expression can be used in equations or further calculations involving the number $x$.