(3x
+ y) - (-x - 4y)=3х+у+х+4у=4х+5у
(x + 6y) - (8x - 7y)=х+6у-8х+7у=-7х+13у
(m + n) - ( m - n)=m+n-m+n=2n
( m + 3) - (6m +5) - (m -1)=m+3-6m-5-m+1=-6m-1
(x - y) + (x - y) -
(2x + y)=x-y+x-y-2x-y=-3y
(0,2x - 3) - ( x - 2) - (0,4x - 1)=0.2x-3-x+2-0.4x+1=-1.2x