Consider the expression 
.
This expression has value 
due to what is called operator precedence (or "order of operations"). Precedence
of common operators is generally defined so that "higher-level" operations
are performed first (i.e., advanced operations "bind more tightly")/ For
simple expressions, operations are typically ordered from highest to lowest in the
order:
1. Parenthesization,
2. Factorial,
3. Exponentiation,
4. Multiplication and division,
5. Addition and subtraction.
For more complex operations, the order of operations depends on the system.
A number of geographically-varying methods for remembering basic precedence rules exist, e.g., PEMDAS in the United States.
