The document explains the order of operations (PEMDAS) for solving mathematical expressions: 1) Parentheses and division bars are solved first from left to right. 2) Exponents are solved next from left to right. 3) Multiplication and division are solved next from left to right. 4) Addition and subtraction are solved last from left to right. It provides examples of solving expressions using PEMDAS and emphasizes the importance of checking your work.