c)10/22+12/22+-24/22+12/11
={(10/22+12/22+(-24/22)}+12/11
=10+12+(-24)/22+12/11
=2/22+12/11
=1/11+12/11
=13/11
d)B=(-1/8)+7/9+(-7/8)+6/7+2/14
={(-1/8)+(-7/8)}+(6/7+2/14)+7/9
=-8/8+14/14+7/9
=(-1)+1+7/9
=0+7/9=7/9
d)D=1/5+(-2/3)+(-1/5)+(-4/9)+2/3
={1/5+(-4/5)}+{(-2/3)+2/3+(-4/9)
=(-3/5)+(-4/9)=(-47/45)
câu6:i)|2x+6|=0
=>2x+6=0
=>2x=(-6)
=>x=(-6):2
=>x=(-3)