Start from zero — the basic math you need before everything else
An inequality compares two things that aren't necessarily equal. The symbols are > (greater than), < (less than), ≥ (greater than or equal to), and ≤ (less than or equal to). So x > 3 means "x is any number bigger than 3".
You solve inequalities almost exactly like equations. Do the same to both sides, keeping the inequality sign instead of an equals sign. There is one special rule: if you multiply or divide both sides by a negative number, you must flip the sign (< becomes >, and vice versa). The solution is a whole range, often drawn as a shaded ray on a number line.
Inequalities show up everywhere as limits. A theme-park ride says you must be taller than 120 cm: height > 120. A road sign says drive at most 30: speed ≤ 30. The answer isn't one number but a whole range — every height above 120, every speed up to 30.
▶ Inequalities