Variable

A variable is a letter that stands for a number you don’t know yet.

Expression

An expression is a math phrase. It has numbers, variables, and operations, but no equals sign.

Equation

An equation is a math statement that has an equal's sign and shows that two things are equal.

Coefficient

The number multiplied by a variable. Example: In 5x, the coefficient is 5.

Linear Equation

An equation whose graph is a straight line. Example: y = 2x + 3

Slope

How steep a line is. Formula: slope = rise/run

8. System of Equations

Two or more equations solved together. Example: x + y = 10 x − y = 2

9. Inequality

A comparison using <, >, ≤, ≥. Example: x > 3