Câu `1: A`
`5/6 + 1/6 : (-5)/12 + (-7)/12`
`= 5/6 + (-2)/5 + (-7)/12`
`= 13/30 + (-7)/12`
`= (-3)/20`
Câu `2: C`
`(-11)/21. 1/5 - (-11)/21. 1/3 + (-11)/21. 2/15`
`= (-11)/21. (1/5 - 1/3 + 2/15)`
`= (-11)/21. 0`
`= 0`
Câu `3: B`
`4/37 + 13/24 + (-5)/31 + (-4)/37 + 11/24`
`= (4/37 + (-4)/37) + (13/24 + 11/24) + (-5)/31`
`= 1 + (-5)/31`
`= 26/31`
