Order of Operations:

To simplify the expression follow the order of operations: (PEMDAS)

1.      Evaluate the expressions inside the Parenthesis/Brackets (P).

2.      Evaluate Powers/Exponents (E).

3.      Multiply and/or Divide in order from left to right (MD).

4.      Add and/or Subtract in order from left to right (AS).

A simple technique for remembering the order of operations is turned into phrase

"Please Excuse My Dear Aunty Sally"

The expression is 

       (Replace a, b, c with 6, 4, 5)

According order of operations inside the grouping symbols should be evaluated first.

First operation is adding the values inside the parenthesis.

                (Add: )

Next operation is multiplication

                  (Multiply: )

Next operation is subtraction

                        (Subtract: )

The value of the expression is 15.