R1 <-> R3, R2-2R1-> R2, R3-3R1->R3 After the three row operations you will get [1 0 1| -1 ] [ 0 1 -1| 1][0 -2 e-3|f+3]. Now we move to the next leading one, which is in R2.
R3+2R2->R3 we get [1 0 1| -1 ] [ 0 1 -1| 1][0 0 e-5| f+5], which is in R.E.F already.
