Subtract 3x−4y−7z from the sum of x−3y+2z and −4x+9y=11z.
sum of x−3y+2z and −4x+9y−11z=x−3y+2z+(−4x+9y−11z)=x−3y+2z−4x+9y−11z=x−4x−3y+9y+2z−11z=−3x+6y−9zNow (−3x+6y−9z)−(3x−4y−7z)=−3x+6y−9z−3x+4y+7z=−3x−3x+6y+4y−9z+7z=−6x+10y−2z