Year 7: Numeric substitution in algebraic expressions

What is Numeric Substitution?

In algebra, you'll often see expressions with letters (variables) like ‘x’, ‘y’, or ‘a’. Numeric substitution means replacing these letters with actual numbers to see what the expression equals.

Example:

Let’s say we have the expression: 2x + 3

If we know that x = 4, we substitute '4' for 'x':

2(4) + 3

Now we perform the calculation:

8 + 3 = 11

So, when x = 4, the expression 2x + 3 equals 11.

Steps for Numeric Substitution:

1. Identify the variable: Find the letter(s) in the expression that represent unknown numbers.
2. Replace the variable: Replace each instance of the variable with the given number.
3. Perform the calculation: Follow the order of operations (BODMAS/PEMDAS) to simplify the expression.

Important Notes:

• Make sure you use the correct sign (+ or -) when substituting the number.
• Carefully follow the order of operations to get the correct answer.