---
title: "Writing Algebraic Equations"
description: "Express missing number problems algebraically using letters for unknowns; translate word problems into equations"
canonical: https://lightmysky.com/learn/mathematics/writing-algebraic-equations-mt_i9rJbuFO3p
source: https://lightmysky.com/learn/mathematics/writing-algebraic-equations-mt_i9rJbuFO3p.md
retrieved: 2026-10-19
---

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# Writing Algebraic Equations

Express missing number problems algebraically using letters for unknowns; translate word problems into equations

Subject: Mathematics · Area: Algebra · Ages 10 to 11
Page: https://lightmysky.com/learn/mathematics/writing-algebraic-equations-mt_i9rJbuFO3p

## Ready when they can

- Write 'I think of a number, double it, and add 5 to get 17' as 2n + 5 = 17
- Solve a one-step equation such as 3x = 24 and explain the reasoning
- Express a word problem as an algebraic equation and find the unknown value

## Lesson: Writing algebraic equations

You already know how to write number sentences with a blank, like 5 + □ = 12. In algebra, you swap the blank for a letter, such as n or x. That letter is called a variable, and it stands for the number you are trying to find.

*(drawing: 'I think of a number' becomes n. 'Double it' becomes 2n. 'Add 5' becomes 2n + 5. 'To get 17' becomes = 17.)*

**Example.** Zara says, 'I think of a number, triple it, and subtract 4 to get 11.' Let n be her number. Tripling means multiply by 3, so the equation is 3n - 4 = 11. Add 4 to both sides: 3n = 15. Divide both sides by 3: n = 5.

*(drawing: 3x = 24 means three equal jumps of x land on 24. Each jump is 24 ÷ 3 = 8, so x = 8.)*

To find the unknown, undo what was done to it. Addition undoes subtraction, and division undoes multiplication. Undo the last operation first.

**Recap.** Turn the words into a letter and symbols, then undo each operation to find the unknown number.

## Practice

17 questions on this page, each with its working shown.

## Needs first

- [Writing Number Sentences](https://lightmysky.com/learn/mathematics/writing-number-sentences-mt_4WaKWECpcv)
- [Order of operations](https://lightmysky.com/learn/mathematics/order-of-operations-mt_jHgRQ4hR0g)
- [Unknown in Multiplication & Division](https://lightmysky.com/learn/mathematics/unknown-in-multiplication-and-division-mt_xZvDCYA5Ae)

## Opens up

- [Advanced Maths Vocabulary](https://lightmysky.com/learn/mathematics/advanced-maths-vocabulary-mt_3rTIyJDw7-)
- [Algebraic Notation](https://lightmysky.com/learn/mathematics/algebraic-notation-mt_KwdjWEmMNo)
- [Solving linear equations](https://lightmysky.com/learn/mathematics/solving-linear-equations-mt_QhFEDyIwSO)
- [Equations with Two Unknowns](https://lightmysky.com/learn/mathematics/equations-with-two-unknowns-mt_YFS7JFk64p)