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]