Solve for X Calculator

Most “solve for x” problems are linear equations in the form ax + b = c: undo the addition, then undo the multiplication. Enter the three numbers and get x with the steps spelled out.

Results

Formula

Isolate x by reversing the operations in the opposite order they were applied:
ax + b = c  →  x = (c − b) ÷ a

How to use this calculator

  1. Rewrite your equation as ax + b = c (move everything else to the right side).
  2. Enter a, b and c with their signs.
  3. Press Calculate and follow the printed steps.
Solve for X Calculator — how the calculation works, illustratedΣ
Solve for X Calculator — how the calculation works, illustrated

Worked example

Solve 3x + 6 = 21.

  1. Subtract 6 from both sides: 3x = 15.
  2. Divide both sides by 3: x = 5.
  3. Check: 3 × 5 + 6 = 21 ✓.

Result: x = 5.

Frequently asked questions

What if x appears on both sides?

First collect the x terms on one side by adding or subtracting the same term from both sides; the equation then fits the ax + b = c form this calculator solves.

What does it mean if a equals zero?

There is no x term left, so the “equation” is just a statement that is either always true (infinitely many solutions) or false (no solution).

How do I check my answer?

Substitute the value back into the original equation. Both sides should come out equal.

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