Пошаговое объяснение:

4/7(2,1m-3 1/4)-3,6(5/9n-0,5n)=

=4/7(2 1/10m-3 1/4)-3 6/10(5/9n-5/10n)=

=4/7(21/10m-13/4)-3 3/5(5/9n-1/2n)=

=6/5m-13/7-18/5((10-9)/18n)=

=6/5×m-13/7-18/5(1/18×n)=

=6/5×m-13/7-1/5×n=1,2m-0,2n-13/7=

=1,2m-0,2n-1 6/7