What is the value of this expression?

2 X { 6 + [ 12 divided ( 3 + 1 ) ] } - 1

3 + 1 = 4 

12 divided by 4 is 3

2 X { 6 + [ 3 ] } - 1

6 + 3 = 9

2 X { 9 } - 1

9 X 2 = 18

18 - 1 = 17!

17 is the answer

I used PEMDAS

P - Parenthesis

E - Exponents

M - Multiplication

D - Division

A - Addition

S - Subtraction

[in order that your supposed to do]