Education
Linear Equation Calculator
Solve a one-variable equation in the form ax + b = c.
Use the tool
Enter your values below. Inputs stay in your browser.
Instant result
Ready
Enter values and calculate
Your result will appear here.
Share this tool
Referencing this tool on a website?
Copy an attribution link. It is optional and does not change free access.
Transparent methodology
What the result includes—and what it does not
Built for students and anyone who needs the value of x in a single first-degree equation written as ax + b = c, and wants the substitution checked.
Calculation method
- 1You supply three numbers: the coefficient a, the constant b on the left side, and the constant c on the right side of ax + b = c.
- 2The solution is evaluated directly as x = (c − b) ÷ a — one arithmetic step, with no iteration, approximation or symbolic algebra.
- 3x is shown to a maximum of 10 decimal places, alongside the equation rebuilt from the three numbers you entered.
- 4A check line substitutes the solution into the left side, so you can compare a × x + b against c; that line rounds at 6 decimal places.
Assumptions and limits
- The equation must already be reduced to the single form ax + b = c. Subtraction is entered as a negative b, and terms sitting on both sides have to be collected before entry.
- a must be non-zero. With a = 0 the equation reduces to b = c, which has either no solution or infinitely many — never one value of x — so the calculator stops instead of returning a number.
- One unknown, first degree only. Systems of equations, quadratics, inequalities, and anything containing x², √x, 1/x or a second variable are outside what this page computes.
- Answers are decimal, not exact fractions or surds, and are rounded for display; a solution of 1/3 is shown as 0.3333333333.
Worked example
Solving 3x + 7 = 25
Input: a = 3, b = 7, c = 25 — the values the page loads with.
Output: x = 6 — because (25 − 7) ÷ 3 = 18 ÷ 3 = 6 — with the check line showing 3 × 6 + 7 = 25.
Primary sources
- Wolfram MathWorld — Linear EquationReference definition of an equation containing only a constant and a first-order term.
- OpenStax, Elementary Algebra 2e — Solve Equations with Variables and Constants on Both SidesUniversity-published open textbook section on collecting terms to reach the ax + b = c form this tool takes.
How to use it
Three steps. One clear answer.
- 1Enter or paste the values requested by the tool.
- 2Review the input units and choose any relevant options.
- 3Calculate, then copy or download the result you need.
Built for trust
Useful without the friction.
- No registration or paywall before your result.
- Responsive controls for phone, tablet, and desktop.
- Clear assumptions and warnings where estimates have limits.
Frequently asked questions
How do you solve an equation in the form ax + b = c?
Subtract b from both sides, then divide by a, which gives x = (c − b) ÷ a. Entering a = 3, b = 7 and c = 25 returns x = 6.
How do I enter an equation that uses subtraction, like 5x − 4 = 11?
Put the minus sign into b and enter it as a negative number: a = 5, b = −4, c = 11. The result is x = 3, because (11 − (−4)) ÷ 5 = 15 ÷ 5 = 3.
What if x appears on both sides, such as 4x + 3 = x + 12?
Collect the x terms and the constants first, then enter the reduced equation. Here 4x + 3 = x + 12 becomes 3x + 3 = 12, so a = 3, b = 3 and c = 12, giving x = 3.
Can it solve systems of equations or quadratic equations?
No. This page solves one unknown of the first degree only. Two equations in two unknowns, or anything with an x² term, needs a different method.
What happens if a is 0?
The calculator asks for a non-zero a. With a = 0 the equation collapses to b = c, so there is no solution when b and c differ and every number is a solution when they match.
Does it give the answer as a fraction or a decimal?
As a decimal, to at most 10 decimal places. A solution of one third is displayed as 0.3333333333 rather than as 1/3.
Keep solving
Related education tools
Grade Calculator
Calculate a percentage and letter grade from points earned and possible.
EducationGPA Calculator
Calculate weighted GPA from course grades and credit hours.
EducationWeighted Average Calculator
Find a weighted mean from paired values and weights.
EducationGCD Calculator
Find the greatest common divisor of two or more integers.
EducationLCM Calculator
Find the least common multiple of two or more integers.
EducationPermutation & Combination Calculator
Count ordered permutations (nPr) and unordered combinations (nCr) for choosing r items from n distinct items.
Education