I'm given his matrix and asked to find the determinant.

Now I do

which gives me this

This eliminates the 5th row and 3rd column.

I'm now left with this:

Now I'm trying to get rid of row and column 1:

Awkward says: here you doubled the determinant.
And now I'm left with this:

Now I can solve this and this is what I get:

That gives me:

This is where I don't understand because the answer in the book is 359, but what about the cofactor of 2 when I eliminated the row and column 1?

Don't I have to multiply everything by 2 which would not be the answer in the book?

Thank you.