Year 7: Numeric Substitution in Simple Algebraic Expressions

What is Numeric Substitution?

Numeric substitution means replacing letter variables with actual numbers in an expression, then calculating the result.

Why do we use it?

• To find the value of an expression for specific numbers
• To check if an equation is true
• To solve real-world problems with formulas

Steps for Numeric Substitution

1. Identify the variable: Find the letter(s) in the expression
2. Replace the variable: Substitute each variable with its given number
3. Calculate: Follow order of operations (BODMAS/PEMDAS) to simplify

Examples

Example 1: Find the value of $2x+3$ when $x=4$

1. Substitute x with 4: $2\left(4\right)+3$
2. Calculate: $8+3=11$

Example 2: Find the value of $3a-2$ when $a=5$

1. Substitute a with 5: $3\left(5\right)-2$
2. Calculate: $15-2=13$

Example 3: Find the value of $x+y$ when $x=2$, $y=3$

1. Substitute: $2+3$
2. Calculate: 5