Letters that stand for numbers
Algebra is just arithmetic with placeholders. A variable like x stands in for a number you don't yet know — and an equation tells you what's true about it.
Variables and constants
A variable is a symbol (often x or y) that holds a number. A constant is a fixed number. In 3x + 7, x is the variable, 3 is the coefficient, 7 is the constant.
Equations
An equation says two expressions are equal. To solve, do the same thing to both sides until the variable stands alone. x + 5 = 12 → x = 7.
Inequalities
Use <, >, ≤, ≥. Solve like equations — but if you multiply or divide by a negative, flip the inequality: −2x > 6 → x < −3.
Functions and graphs
A function takes an input and produces one output. The graph of y = mx + b is a straight line — slope m, y-intercept b.
Headline rules
Hands-on tools
Solve on a balance, slide a line, or translate a story into algebra.
Balance scale solver
Whatever you do to one side, do to the other. Click an operation to apply.
Slope-intercept playground
Drag the sliders. The line and equation update together.
Inequality grapher
Pick a comparison and a value. Open dot for strict, closed dot for ≤ or ≥.
x < 3 — every x to the left of 3 (open dot, value 3 not included).
Word problem translator
Highlighted phrases map to algebra. Click a phrase for a hint.
Quiz
Flashcards
Tap a card to flip. ← / → keys to navigate.
Daily challenge
A new problem every day. Same problem for everyone, worldwide. Build a streak — one shot per day.
For teachers
Print-ready worksheet, answer key, teaching tips and standards alignment.
Teaching tips
Standards alignment
Reference
Formula sheet
Photo gallery
Images sourced from Wikipedia.