Solve for x: Beginner’s Guide With Practice Problems
Updated · By the SolverCalc team
Quick answer
Use the inverse operation to get x by itself: add ↔ subtract, multiply ↔ divide.
“Solve for x” means find the number that x stands for. Think of an equation as a balanced scale. To find x, you remove everything around it, one step at a time, while keeping both sides balanced.
Inverse operations
- Addition is undone by subtraction.
- Subtraction is undone by addition.
- Multiplication is undone by division.
- Division is undone by multiplication.
One-step equations
| Equation | Inverse step | Answer |
|---|---|---|
| x + 9 = 15 | Subtract 9 from both sides | x = 6 |
| x − 4 = 10 | Add 4 to both sides | x = 14 |
| 7x = 56 | Divide both sides by 7 | x = 8 |
| x ÷ 3 = 12 | Multiply both sides by 3 | x = 36 |
Two-step equations
- Start with 2x + 5 = 17.
- Undo the addition first: subtract 5 from both sides to get 2x = 12.
- Undo the multiplication: divide both sides by 2 to get x = 6.
- Check: 2 × 6 + 5 = 17. ✓
Another example: x/4 + 3 = 9. Subtract 3 to get x/4 = 6, then multiply by 4 to get x = 24. Check: 24 ÷ 4 + 3 = 9. ✓
Notice the pattern: you undo operations in the reverse order of PEMDAS—addition and subtraction first, then multiplication and division.
Tips for getting it right
- Write each step on a new line so you can spot mistakes.
- Pay attention to negative signs; −x = 5 means x = −5.
- Always plug your answer back into the original equation.
Once these basics feel comfortable, move on to equations with variables on both sides in our guide to solving linear equations.
Practice set
| Equation | Answer |
|---|---|
| x + 12 = 30 | x = 18 |
| 9x = 63 | x = 7 |
| 3x − 4 = 20 | x = 8 |
| x/2 − 1 = 6 | x = 14 |