RREF is the abbreviation for Reduced Row-Echelon Form.
For the given RREF, the standard form system of equations is
1*x - 1*y = 0
0*x + 0*y = 1
Since in the second equation, left side is 0 (zero) at any values x and y, while right side is 1 (one),
the given system of equations HAS NO solutions. ANSWER