This document discusses mathematical equations and variables. It explains that a variable can represent any quantity that can change value in an equation. Common variables are x and y. The document also covers order of operations using PEMDAS (Parentheses, Exponents, Multiplication, Division, Addition, Subtraction) to determine the proper sequence to evaluate terms in an equation. Following PEMDAS is important as it tells us the order to follow when an equation contains multiple operations. An example problem demonstrates applying PEMDAS to solve an equation step-by-step.