Solve for X Calculator

Q: What does “solve for x” mean?

It means rearranging the equation until x is on its own on one side, such as x = 3. The other side is the value (or expression) that x equals.

Q: How do I solve for y?

The same way as for x: undo each operation around y, doing the same thing to both sides. In 2x + 3y = 6, subtract 2x, then divide by 3 to get y = 2 - 2/3x.

How to use the variable solver

Type the letter you want in the “Solve for” box — x is already there — then type the equation or formula, such as “2x + 3y = 6”.
Press Solve. Sumzo undoes each operation in turn until the variable is on its own.
With other letters in the equation (a formula), the answer is written in terms of those letters.
Read the check at the end, or ask “Why?” about any step.

Worked examples

Easy: find $x$ in $7x + 4 = 25$

Subtract 4 from both sides: $7x = 21$ .
Divide both sides by 7: $x = 3$ .
Check: $7(3) + 4 = 25$ ✓.

Medium: find $y$ in $2x + 3y = 6$

Subtract $2x$ from both sides: $3y = 6 - 2x$ .
Divide both sides by 3: $y = \frac{6 - 2x}{3} = 2 - \frac{2}{3}x$ .
Check with $x = 3$ : the formula gives $y = 0$ , and $2(3) + 3(0) = 6$ ✓.

Hard: find $r$ in the formula $A = \pi r^2$

Divide both sides by $\pi$ : $r^2 = \frac{A}{\pi}$ .
Take the square root. A radius can’t be negative, so keep the positive root: $r = \sqrt{\frac{A}{\pi}}$ .
Check: $\pi \left(\sqrt{\frac{A}{\pi}}\right)^2 = \pi \cdot \frac{A}{\pi} = A$ ✓.

Common mistakes when isolating a variable

Undoing operations in the wrong order. Undo addition and subtraction before multiplication and division.
Dividing only one term: from $3y = 6 - 2x$ , divide the whole right side by 3, not just the 6.
Forgetting the negative root. $x^2 = 9$ gives $x = 3$ or $x = -3$ ; drop the negative one only when it makes no sense, like a length.
Changing the other letters. In a formula, letters such as $x$ or $\pi$ stay in the answer — only the variable you are solving for moves.

よくある質問

What does “solve for x” mean?

It means rearranging the equation until $x$ is on its own on one side, such as $x = 3$ . The other side is the value (or expression) that $x$ equals.

How do I solve for y?

The same way as for $x$ : undo each operation around $y$ , doing the same thing to both sides. In $2x + 3y = 6$ , subtract $2x$ , then divide by 3 to get $y = 2 - \frac{2}{3}x$ .

Can it isolate a variable in a formula?

Yes. Type the formula and the letter you want, for example “Solve for h: V = πr²h”. The answer is given in terms of the other letters, here $h = \frac{V}{\pi r^2}$ .

Does it work for other letters, like u?

Yes — any letter. For example “Solve for u: v = u + at” gives $u = v - at$ .

Does the solve for x calculator show steps?

Yes. Each step says what was done to both sides, and the answer is checked by substituting it back where possible.

Where can I practise solve for x problems?

Try the linear equations topic in Practice: new questions every time, with hints and worked solutions.