Solve for X
Free pre-algebra game: solve one-step equations like x + 7 = 15 and 3x = 21 in your browser. For grades 6+. No download, no sign-up.
Grade 6+ · Free · No sign-up
How to play & why it works
Rounds serve one-step equations — x + 7 = 15, 3x = 21, x − 4 = 9 — and you type the value of x. No symbol shuffling, no notebooks: just the core question "what number makes this true?" over and over until it feels obvious.
One-step equations are the front door of algebra, and learners who meet them as puzzles about numbers (rather than rules about moving symbols) carry that number-sense into every later topic. The equation x + 7 = 15 is, at heart, a missing-number fact — the same thinking this game family has been building since number bonds.
The move to internalize: undo the operation. Addition undoes subtraction, division undoes multiplication. Say it as a question — "3 times what is 21?" — and notice that arithmetic fluency is doing all the real work.
The free MathIt app continues into inequalities, powers and multi-step mental chains, with an adaptive ladder that meets each learner where they are.
One-step equations are where algebra either clicks or becomes a ritual. The idea is small: whatever was done to x, undo it on both sides. Addition is undone by subtraction, multiplication by division. Students who learn that principle can solve equations they have never seen; students who memorise 'move it over and flip the sign' are lost the first time an equation looks unfamiliar.
Checking is half the skill. Substituting the answer back — if x = 8, does 3x = 24? — catches nearly every sign error, and it is the habit that makes multi-step equations survivable a year later.
Skills you'll practice
Keep practicing
Frequently asked questions
What is a one-step equation?
An equation solved by a single inverse operation, like x + 7 = 15 or 3x = 21. Multi-step equations chain several of these together, so this is the foundation for all of them.
What does 'solve for x' actually mean?
Find the number that makes the statement true. In x − 4 = 9, x = 13 because 13 − 4 really does equal 9. Everything else in algebra is machinery for finding that number efficiently.
What grade is solving for x?
Typically sixth or seventh grade, though one-step equations often appear earlier as missing-number problems. If a student is comfortable with missing factors, they are ready for this.
Get the full game
Adaptive difficulty, daily streaks, and live 2–5 player math battles — free on iOS and Android.