GCSE Maths: Substitution
Replace letters with numbers and evaluate the expression correctly. Practise it with adaptive questions for AQA, Edexcel, OCR and Eduqas.
What you need to know
The concepts examiners test on substitution, and what each one is really asking.
Where marks get lost
The exam technique that separates a correct method from a correct answer.
- Writing -3² and getting -9, when (-3)² is 9 — always bracket a negative before squaring
- Reading 3a as "3 then a" rather than 3 multiplied by a
- Adding before multiplying, ignoring BIDMAS once the numbers are in
- Losing a minus sign when substituting a negative value
Substitution questions students ask
Is Substitution on the Foundation paper?
Yes. Substitution appears at both Foundation and Higher tier, though Higher papers take it further.
What should I know before starting Substitution?
It builds on Order of operations (BIDMAS) and Negative numbers and Algebraic notation. If those feel shaky, practise them first — Substitution questions assume them.
What is the most common mistake in Substitution?
Writing -3² and getting -9, when (-3)² is 9 — always bracket a negative before squaring.
Which exam boards cover Substitution?
All four we support — AQA, Edexcel, OCR and Eduqas. GCSE Maths subject content is set by the DfE, so the topic is common to every board; what changes is the paper structure and the grade boundaries.