Ответ: 1) (3x+y)-(x-4y)=3x+y-x+4y=2х+5у2) (x+6y)-(8x-y)=x+6y-8x+y=-7х+7у3) (m+n)+(m-n)=m+n+m-n=2m4) (6m+5)-(m-1)=6m+5-m+1=5m+65) (2x+y)-(x+y)=2x+y-x-y=х6) (2m-3n)+(2m+3n)=2m-3n+2m+3n=4m