Two-Step Equation Calculator
Solve equations of the form ax + b = c, with each step shown and the answer checked.
x equals
5
- The equation
- 3x + 5 = 20
- Step 1
- Subtract 5 from both sides: 3x = 15
- Step 2
- Divide both sides by 3: x = 5
- Check
- 3(5) + 5 = 20, which matches 20
The solution is x = 5.
Calculation breakdown
| Step | Formula | Result |
|---|---|---|
| After undoing b | 20 − (5) | 15 |
| After dividing by a | 15 ÷ 3 | 5 |
How it works
Enter a, b and c for the equation ax + b = c. Choose the minus sign for ax − b = c.
Worked example
3x + 5 = 20:
- Subtract 5 from both sides: 3x = 15
- Divide both sides by 3: x = 5
- Check: 3 × 5 + 5 = 20 ✓
Sources
Frequently asked questions
What is a two-step equation?
It is an equation that takes two operations to solve for the unknown, such as 3x + 5 = 20. You undo the addition or subtraction first, then the multiplication.
How do you solve ax + b = c?
Subtract b from both sides to get ax = c − b, then divide both sides by a. For 3x + 5 = 20, subtract 5 to get 3x = 15, then divide by 3 to get x = 5.
What if the equation has a minus, like 2x − 7 = 11?
Add 7 to both sides instead. 2x = 18, then x = 9. Choose the minus sign in the calculator to enter this form.
Why can't a be zero?
If a is 0, the x term disappears and the equation is either always true or never true, so there is no single value of x to find.
How can I check my answer?
Put the answer back into the original equation. For x = 5, 3(5) + 5 = 20, which matches the right side. The calculator shows this check.