Work from the outside inward
For ax + b = c, undo the addition by subtracting b from both sides, then undo multiplication by dividing by nonzero a. A negative b means subtracting a negative number, which adds its magnitude.
Expand brackets first if needed. Apply a multiplier to every term inside a bracket; a missed constant is a common source of an answer that looks plausible but fails substitution.
Keep the domain and the answer in view
This method applies to a linear equation with a nonzero coefficient. If x appears in a denominator or under a radical, additional restrictions and checks are required beyond the linked solver.
After solving, replace x in the original equation. When x stands for a length or count, also check whether the resulting sign or fractional value makes sense in context.
Undo subtraction with addition
In 5x − 9 = 16, the outside operation subtracts 9. Undo it by adding 9 to both sides, giving 5x = 25, then divide by 5. The instruction to “move the 9” is less informative than naming the inverse operation. Explicit operations make the same method work reliably with positive or negative coefficients.
LET’S WORK IT THROUGH
Solve −3x + 8 = 23.
- Subtract 8: −3x = 15.
- Divide both sides by −3.
- Check −3 × (−5) + 8 = 23.
THE ANSWERx = −5.
YOUR TURN
A small check for understanding.
Solve 2(x + 4) = 18.
Reveal the answer
x = 5. Expand to 2x + 8 = 18, subtract 8, then divide by 2.
Now try your own numbers.
The solve for x includes input guidance and the limits of its supported calculations. Use it alongside the method above.
Open Solve for x ↗A note on precision: preserve exact fractions where possible and round numerical results at the end. Found an unclear step? Prepare a correction report.