A system of linear equations can have no solution, a unique solution or infinitely many solutions. A system has no solution if the equations are inconsistent, they are contradictory. for example 2x+3y=10, 2x+3y=12 has no solution. is the rref form of the matrix for this system.
This is in my opinion. Im not sure if it is correct or not but Good luck!
The third one :) I hope I did it right
