Help with Determinants
If you open the determinants along the middle column, we get for the first determinant:

$ -(bf-ec) + (af-cd)  -(ae-bd) = -3$ $\hspace{1cm}$ $ [1]$

And for the second determinant, we get

$-(bf-ec) + 2(af-cd)  -3(ae-bd) = -2 $ $\hspace{1cm}$ $ [2]$

The required determinant is

$  2(af-cd)  -4(ae-bd) $ $\hspace{1cm}$ 

Which is just $2*([2] - [1])$, which boils down to $2$.