The determinant of a 2 x 2 matrix can be calculated as:
Product of non-diagonal elements subtracted from product of diagonal elements.
The diagonal elements in given matrix are 12 and 2. The non-diagonal elements are -6 and 0.
So,
Determinant G = 12(2) - (-6)(0)
Determinant G = 24 - 0 = 24
So, option B gives the correct answer