4/9*(2,7m-2.1/4n)-4,2(5/7m-0,5n)
4/9*(2,7m-2.1/4n)-4,2(5/7m-0,5n)= 4*0,3m-21/9n-0.6*5m+2.1n=1.2m-7/3n-3m+2.1n=
-1.8m-7/3n+21/10n=
133/30n - 1.8m