Lesson 5: Solving One-Step Equations
An equation has an equals sign — it says two expressions are equal. Solving means finding the value of the variable. The golden rule: whatever you do to one side, do to the other.
Key Concepts
Balance Model
Think of an equation as a balance scale. x + 5 = 12. Both sides balance. To solve: subtract 5 from BOTH sides. x + 5 - 5 = 12 - 5. x = 7. Always maintain balance.
Inverse Operations
Addition ↔ subtraction. Multiplication ↔ division. To undo an operation, apply its inverse to both sides. x - 8 = 3 → add 8. x + 8 = 3 → subtract 8. 3x = 12 → divide by 3. x/4 = 5 → multiply by 4.
Checking Solutions
Substitute your answer back into the original equation. If x = 7: x + 5 = 12 → 7 + 5 = 12 → 12 = 12 ✓. Checking takes 5 seconds and prevents errors.
Writing Equations
Many word problems translate directly. 'A number increased by 6 equals 14' → n + 6 = 14. 'Three times a number equals 21' → 3n = 21. Practice translating words to math.
🔬 Interactive Lab: Solving One-Step Equations Lab
✅ Check Your Understanding
1. To solve x + 9 = 15, you should:
2. Solve: 5x = 35
3. Solve: x/4 = 6