1. **Problem Statement:** We are given algebraic expressions and values for variables, and we want to evaluate these expressions step-by-step. 2. **Evaluating an expression:** When you have an expression like $2y + 3$ and a value for $y$, substitute the value into the expression. 3. **Example 1:** Evaluate $2y + 3$ where $y = 7$. Substitute $y$: $$2(7) + 3$$ Multiply: $$14 + 3$$ Add: $$17$$ 4. **Simplifying expressions:** For $9x - 3x - 10$, combine like terms (terms with $x$). Combine $9x$ and $-3x$: $$9x - 3x = \cancel{9x} - \cancel{3x} = 6x$$ So the expression becomes: $$6x - 10$$ 5. **Addition in algebra:** Addition is commutative, meaning order does not matter. Examples: $$3 + 5 = 8 \quad \Rightarrow \quad 5 + 3 = 8$$ $$y + 5 = 5 + y$$ $$8 + y + 10 = 10 + y + 8$$ 6. **Multiplication in algebra:** Multiplication is also commutative. Examples: $$5y = y5$$ $$5 \times 3 = 15$$ $$3 \times 5 = 15$$ 7. **Summary:** To evaluate expressions, substitute values, perform multiplication and addition, and combine like terms carefully. Remember addition and multiplication can be done in any order. Final answer for the first evaluation: $17$.