Algebra
A letter is just a box holding a number you don't know yet.
Using letters in mathsSubstitutionSimplifying expressionsMore complex substitution
📖 Learn
Letters = numbers
3a means 3 × a. If a = 5, then 3a = 15.
Substitution
Swap the letter for its value, then calculate.
Collect like terms
2x + 3x = 5x, but 2x + 3y stays as it is — they're different 'fruits'.
Worked example
If x = 4, find 2x + 7
- 12x means 2 × x
- 22 × 4 = 8
- 38 + 7 = 15 ✅
⭐ Practise
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