If you have:
The cofactor for is the determinant of:
The cofactor for is negative(-) of the determinant of:
The cofactor for is the determinant of:
Why are you being asked to do a "co-factor expansion" if you don't know what that is?
I would recommend starting your co-factor expansion using the first column. That way you just have 2 times and expand that determinant on the second column. Do you see why?