Ответ:

  1. \(4x-6y-3x+5y=(4-3)x+(-6+5)y=x-y\).
  2. \(7y-9y+2x+2y=2x+(7-9+2)y=2x\).
  3. \(y-2x-y+x=(-2+1)x+(1-1)y=-x\).
  4. \(0.3y-0.1x-0.9x+0.7y=(-0.1-0.9)x+(0.3+0.7)y=-x+y=y-x\).
  5. \(\frac12x-2.8y-0.2x+\frac45y=(0.5-0.2)x+(-2.8+0.8)y=0.3x-y\).
  6. \(-\frac53y+1.5x+1.6y-0.5x=(1.5-0.5)x+(-\frac53+\frac85)y=x-\frac1{15}y\).
  7. \(\frac13y-\frac13x+\frac13y+\frac13x+\frac13y=y\).