Write down the elementary matrix E such that the matrix EA is obtained from A when:

the third row of A is replaced by (row three of A - 2 x row one of A ).

So I dont know where to start with this. I tried Letting A equal an example matrix, Then EA = The matrix after the stated operation. Then E = A/EA and therefore

E = (EA)^-1 (A). Am I on the right track? Unfortunately I dont think my EA matrix was even invertible. Im lost! :(

Any help is much appreciated.