This document discusses rules for simplifying mathematical expressions. It explains that "of" should be replaced with multiplication and "divided by" should be replaced with division. It also emphasizes following the order of operations using VBODMAS (Vincules, Brackets, Of, Division, Multiplication, Addition, Subtraction). Some additional rules covered include performing the operation on the left first if of equal precedence, and rounding decimal numbers to the nearest integer when simplifying expressions.