It's the method your using.
you're using the flawed PEMDAS method.
PEMDAS in that order......
Paraphases
Exponents
Multiplication and
Division(left to right)
Addition and
Subtraction(left to right)
The Order of Operations: More Examples
see example 2.....
The PEMDAS system has been mis-taught in some schools for a couple decades now. Even math teachers will argue of order of operations because the centuries long held, scientific method, which is what I described, involves eliminating the paraphrases first, which is what is used in the sciences. Reason being is 2(2+1) stays 2(3) until you do so. 2(3) is equal to 2x3. This is the same as if you were solving for x, and 2x, where the number in front is multiplying what is in the phases. The scientific method states that you solve inside the Paraphases, then any Paraphases Exponents and then any Multiplication/Division of the Paraphases then moving on to Multiplication, Division,Addition,Subtraction. Which is why "Scientific" calculators will give you a different answer than a Algebraic/Graphing calculator.
So the problem is that there's two sides arguing over the "correct" order of operation, thus the teaching of two different methods.