а) 7/8*(4-x)-(3/4+x)= 7/8*4-7/8*х-3/4-х=7/2-7/8*х-3/4-х=-15/8*х+11/4

б) -(3/19-y)-1/2(y+2/19)= -3/19+у-1/2*у-1/2*2/19= -3/19+1/2*у-1/19= -4/19+1/2у

в) -7/13*(26/27+x)-(4/9-x)= -7/13*26/27-7/13*х-4/9+х= -14/27+6/13*х-4*3/(9*3)=-14/27-12/27+6/13*х= -26/27+6/13*х

г) -(1/16-y)+3/4(1/8+y)= -1/16+у+3/4*1/8+3/4*у= -1*2/(2*16)+7/4у +3/32= 1/32+7/4у