I am doing this problem assuming that you mean to solve for m and n as x and y do not exist in this system of equations.
-4m+2n=6
-4m+n=8
We can see that the coefficient of x for both equations are -4; therefore, elimination with subtraction is possible.
First equation - second equation
n=-2
Then substitude back in to solve for m
-4m+(-2)=8
4m=10
m=5/2
Therefore the answer is
n= - 2
m= 5/2
I hope this helped and if you have any questions please ask.