Substituting Values for a Variable

Definition and Core Concept

• Substituting Values for a Variable:
  • When given a number phrase with a variable (a letter used to represent a number), a specified quantity can be substituted in place of that variable.

Worked Examples of Variable Substitution

• Addition Example:

  • Given: $x = 4$
  • Expression: $x + 6$
  • Substitution: $x + 6 = 4 + 6 = 10$
  • Explanation: The number $4$ is substituted for the variable $x$.

• Multiplication Example:

  • Given: $y = 7$
  • Expression: $4y$
  • Substitution: $4y = 4(7) = 28$
  • Explanation: The number $7$ is substituted for the variable y$.\n * **Note:** The notation 4y$means$4$times$y$($4 \times y).\n\n* **Subtraction Example:**\n * **Given:** w = 5\n * **Expression:** w - 2\n * **Substitution:** w - 2 = 5 - 2 = 3\n * **Explanation:** The number 5$is substituted for the variable$w$.

• Division Example:

  • Given: $b = 12$
  • Expression: $\frac{b}{3}$
  • Substitution: $\frac{b}{3} = \frac{12}{3} = 4$
  • Explanation: The number $12$ is substituted for the variable $b$.