Đáp án:
a) `49/30`
b) `91/36`
c) `11/56`
d) `1/72`
Giải thích các bước giải:
a) `text{BCNN : 30}`
`11/15 + 9/10 = 22/30 + 27/30 = (22+27)/30 = 49/30`
b) `text{BCNN : 72}`
`5/6 + 7/9 + 11/12`
`= 60/72 + 56/72 + 66/72 = (60+56+66)/72`
`= 182/72 = 91/36`
c) `text{BCNN : 168}`
`7/24 - 2/21 = 49/168 - 16/168`
`= (49-16)/168 = 33/168 = 11/56`
d) `text{BCNN : 72}`
`11/36 - 7/24 = 22/72 - 21/72`
`= (22-21)/72 = 1/72`
