8 4/9-m=3 7/9
8 4/9-3 7/9=m
7 13/9-3 7/9=m
4 6/9=m
4 2/3=m
проверка
8 4/9-4 2/3=3 7/9
8 4/9-4 6/9=3 7/9
7 13/9-4 6/9 =3 7/9
3 7/9=3 7/9