Order of operations
Order of operations is an order, agreed upon by mathematicians, for performing operations to simplify expressions. This order is as follows:
 Perform all operations within parantheses or other grouping symbols
 Simplify expressions involving exponents
 Multiply and divide in order from left to right
 Add and subtract in order from left to right
This is commonly taught as the mnemonic "Please excuse my dear aunt Sally," abbreviated as PEMDAS, which can help a person remember the order of operations: parantheses, exponents, multiplication, division, addition, and subtraction, listed in order of decreasing priority, with multiplication and division, and addition and subtraction having equal priority. Refer below for some examples:
Examples
Ex 1  


Ex 2  
