What are the rules of simplifying numerical expression?

To simplify numerical expressions, follow the order of operations, often remembered by the acronym PEMDAS: Parentheses, Exponents, Multiplication and Division (from left to right), Addition and Subtraction (from left to right). Combine like terms by adding or subtracting coefficients of the same variable. Additionally, reduce fractions to their simplest form by dividing the numerator and denominator by their greatest common factor. Always ensure the expression is in its simplest and most concise form.