Please Excuse My Dear Aunt Sally and P - Please Excuse My...

Please Excuse My Dear Aunt Sally and P-E-M-D-A-S are mnemonic devices for the
order in which an algebraic equation be solved or simplified. PEMDAS stands for:
parenthesis, exponents, multiplication, division, addition, and subtraction. The letters
'M' and 'D' are underlined because the order in which multiplication and division are to
be solved is from left to right in the equation (in the order that they come). The same
concept holds true for subtraction and addition, which is why the letters 'S' and 'A' are
also underlined in the previously stated mnemonic devices. 'M' and 'D' are equivalent to
each other and 'S' and 'A' are equivalent to each other.