Algebraic Conversions and Substitution

Converting Words into Algebra

• In algebra, letters represent numbers; these letters are called variables.

• The term "any number" can be represented by a variable.

• An algebraic expression example: "n+5"

• A variable's value can change or vary.

Substitution

• Substitution in algebra means replacing a variable (letter) with a number to solve the expression.

• Replace pronumerals with their given values.

Example:

If $a = 1$, evaluate the expression $9 + 2b$ when $b = 3$.

$9 + 2b = 1 + 2 \times 3$

$= 1 + 6$

$= 7$

Examples: Write an algebraic expression for the result of each statement

a) Think of a number (n), multiply it by 3, and then subtract 5.

$n \times 3 - 5 = 3n - 5$

b) Think of a number (n), subtract 5, and then multiply by 3.

$(n - 5) \times 3 = 3(n - 5)$