Q1.

Question

Suppose A= ( -1 2 -3
-4 3 2
1 3 1 ), then the determinant of this matrix is?

Q2.

Suppose det ( 1 2 3
1 4 5
y 4 5)=0, then y=?

Answer 1

So where is your attempt to do this?
There are two common ways, I do not even know which you are using since I see no work.