-3/4(1/3m+n)-1/4(3m+n)=
-3/4(1/3m+n)-1/4(3m+n)=-1/4 m-3/4n-3/4m-1/4n=-1/4m-3/4m-3/4n-1/4n=-m-n; Ответ:-m-n
-0.25m-0.75n-0.75m-0.25n=-0.1m-0.1n