What eigen value for this matix
(1 -2)
(-2 0)

You find the eigenvalues of a matrix A by following these steps:

So, in this case, we have

The determinant of this matrix is

Finally, we have

So, the two eigenvalues are

distance covered by pamela in 9 l of fuel = 99km

let us apply unitary method here.

distance covered by pamela in 1 l of fuel =99/9 =11 km

now let us find distance covered by pamela if she has 12 l of fuel.

distance covered in 12 l = distance covered in 1 l of fuel * 12

we know that distance covered by here in 1 l is 11 km.

so distance covered in 12 l of fuel = 11*12 = 132 km.