Algebra
A letter stands for a number we haven't found yet.
Simple formulaeLinear sequencesMissing numbersTwo unknowns
📖 Learn
Formulae
Cost = 3n + 2 means 3 lots of n, plus 2.
Sequences
Find the jump between terms — that's the rule.
Missing numbers
□ + 7 = 15? Undo it: 15 − 7 = 8.
Worked example
Solve 4n − 3 = 25
- 1Add 3: 4n = 28
- 2Divide by 4: n = 7 ✅
⭐ Practise
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