А) 3m+2m+4m=9m
б) 1/2а+1/3а-1/6а=3/6а+2/6а-1/6а=4/6а=2/3а
в) 0,9b-1,3b+0,7b=0,3b
г) х-0,2х-0,7х=1х-0,2х-0,7х=0,1х
д) 1/12m-1/4m-1/3m=1/12m-3/12m-4/12m=-6/12m=-1/2m
е) с-0,8с-1/5с-1/2с=10/10с-8/10с-2/10с-5/10с=-5/10с=-1/2с
ж) 0,3а-0,2b-0,7а+0,2b=-0,4а
з)4а-6а-2а+12-11=-4а+1
и) 2/3а+3/8b-1/6a-1/4b=(4/6a-1/6a)+(3/8b-2/8b)=3/6a+1/8b=1/2a+1/8b
к) 5/7k-2/3-3/14k-1/3=(10/14k-3/14k)+(-2/3-1/3)=7/14k-3/3=1/2k-1
л) 0,2m-2/9-4m+5/9=(0,2m-4m)+(-2/9+5/9)=-3,8m+3/9=-3,8m+1/3
м) 1/2а+1/3с-1/2а+2/3с=(1/2а-1/2а)+(1/3с+2/3с)=0+3/3с=1с=с