9/11 + 8/15 + 13/11 + 7/15 =(9/11 + 13/11) + (8/15 + 7/15) = 22/11 + 15/15 = 2+1 =3
(9/11+13/11)+(8/15+7/15)=22/11+15/15=2+1=3
= [ 9/11 + 13/11] + [ 8/ 15 + 7/15 ]
= 22/11 + 1
= 22/11 + 1/1 = 22/11 + 11/11
= 33/11
Đề bài : 9/11 + 8/15 + 13/11 + 7/15=?
(9/11 + 13/11) + (8/15 + 7/15)=
24/11 + 1 = 35/11