Think of a formula like a recipe. If a cake recipe says "2 × eggs + 100g flour", you substitute in the actual number of eggs to work out how much flour! Substitution in maths is the same - you replace the letters (variables) with actual numbers to calculate an answer.
This introduction covers What is Substitution? within Simplifying Expressions for GCSE Mathematics. Revise Simplifying Expressions in Algebra for GCSE Mathematics with 11 exam-style questions and 5 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 8 of 19 in this topic. Use this introduction to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Simplifying Expressions
Which two terms are like terms?
Explain why 3x + 2x² cannot be simplified to 5x³.
Quick recall flashcards
Substitution
Replace each letter with its given value, then calculate
Like Terms
Terms with same letter and power: 2x and 5x are like terms