Swap the 1st and the 2nd rows inversing determinant sign Divide the 1st row by 54 Multiply the 1st row by 33 Subtract the 1st row from the 3rd row and put the 1st row back as it was Divide the 2nd row by 12 Multiply the 2nd row by 5 Subtract the 2nd row from the 3rd row and put the second row as it was Multiply the main diagonal numbers A= -(54)(12)(-35/12)(0)(0)= 0