PEMDAS and it is used to be sure everyone gets the same answer for a series of calculations.
When there are several calculations in an expression, especially if there are different operations, people could get different answers depending on where they start. Using PEMDAS, there is only one correct answer for any expression.
PEMDAS stands for doing operations in any calculation in this order, from left to right:
Parentheses
Exponents
Multiplication and Division (all, in order from left to right)
Addition and Subtraction (all, in order from left to right)
It is easily remembered using the mnemonic “Please Excuse My Dear Aunt Sally.”