Substitute a value
- Replace the letter with the number.
- Use brackets for negative numbers.
- Calculate using order of operations.
Answer: 3a - 1 when a = 4 is 11
𝑥 Algebra
Substitution
Learn substitution with a GCSE-style explanation, help guide, worked example, practice question and flashcards.
Global XP
Level 10 / 100 XP
1. Explanation
Key idea
- Substitution is part of algebra and appears often in KS3–GCSE maths.
- Substitution means replacing letters with numbers.
- Use the worked model, help guide, interactive question and flashcards to practise substitution until the steps feel automatic.
Real-life examples
- Shopping, sport, travel, science, design and everyday decisions all use this skill.
2. Visual
Substitution learning map
Understand the key idea → follow the help guide → practise a question → check your method → build speed with flashcards.
3. Help guide
How to tackle Substitution
- Learn the rule: Substitution means replacing letters with numbers.
- Worked model: Replace the letter with the number. Use brackets for negative numbers. Calculate using order of operations.
- Try the interactive question without looking at the answer first.
- Use the flashcards to test the rule, the method and a common check.
4. Worked examples
Step-by-step working
5. Interactive questions
Try it yourself
Find 2x + 3 when x = 5.
6. Flashcards
Master quick recall
Flip each card, then choose whether you know it or need more practice.
0 mastered
FrontRule for Substitution
BackSubstitution means replacing letters with numbers.
FrontExample answer: Find 2x + 3 when x = 5.
Back2 × 5 + 3 = 10 + 3 = 13.
FrontCommon check for Substitution
BackCheck units/notation, compare with an estimate, and make sure the answer matches the question.
7. Finish
Complete this topic
When you have read the examples, tried the question and reviewed flashcards, claim your topic completion XP.