Two real numbers or two algebraic expressions related by the symbols <, >, ≤ or ≥ form an inequality.

Equal numbers may be added to (or subtracted from ) both sides of an inequality.

Both sides of an inequality can be multiplied (or divided ) by the same positive number. But when both sides are multiplied (or divided) by a negative number, then the inequality is reversed.

The values of x, which make an inequality a true statement, are called solutions of the inequality.

To represent x < a (or x > a) on a number line, put a circle on the number a and dark line to the left (or right) of the number a.