в)5/7*(2,8с-4 1/5 d)-2,4*(5/6с-1,5d)=
5/7*2целых 8/10с=5/7*28/10c=2с
5/7*(-4целых1/5d)=5/7*(-21/5d)=-3d
-2целых4/10*5/6с=24/10*5/6=-1,5
-2,4*(-1,5d)=3,6d
2c-3d-1.5c+3.6d=0.5c+0.6d
d)5/9*(3,6a-3 3/5b)-3,5*(4/7a-6,26b)
5/9*3.6a=36/10*5/9=3a
5/9*(-3целых3/5b)=18/5*(-5/9b)=-2b
-3.5*4/7a=-35/10*4/7=-2a
-3.5*(-6.26b)=21.91b
3a-2b-2a+21.91b=a+19.91b