Evaluating Expressions by Substitution (Grade 6)
To evaluate an expression, replace each letter with its given value and then do the arithmetic, following the order of operations. If n = 4, then 2n + 3 means 2·4 + 3 = 11. Substitution is the bridge between a general rule (with letters) and a specific answer (with numbers) — and it's how you check a solution.
Understanding evaluating expressions by substitution
To evaluate an expression, replace each letter with its given value and then do the arithmetic, following the order of operations. If n = 4, then 2n + 3 means 2·4 + 3 = 11. Substitution is the bridge between a general rule (with letters) and a specific answer (with numbers) — and it's how you check a solution.
Key Idea
To evaluate an expression, replace each letter with its given value and then do the arithmetic, following the order of operations. If n = 4, then 2n + 3 means 2·4 + 3 = 11. Substitution is the bridge between a general rule (with letters) and a specific answer (with numbers) — and it's how you check a solution.
Seeing it in action
Worked example
Evaluate 3a + 2 when a = 5.
Replace a with 5: 3·5 + 2.
Multiply first: 15 + 2 = 17.
Substitute first, then compute.
Try a few
Evaluate x − 6 when x = 10
Evaluate 2(b + 1) when b = 3
Evaluate 4m when m = 7
Function Foundry
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Put the reasoning on paper.
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