Đáp án:
$\\$
`a,`
`3/7 - 5/2 -3/5`
`= 30/70 - 175/70 - 42/70`
`= (30-175-42)/70`
`= (-187)/70`
`b,`
`2/3 - [ (-7/4) - (1/2 + 3/8)]`
`= 2/3 - [-7/4 - (4/8 + 3/8)]`
`= 2/3- [-7/4 - 7/8]`
`= 2/3 - [-14/8 - 7/8]`
`= 2/3 - (-21)/8`
`= 16/24 + 63/24`
`= (16+63)/24`
`= 79/24`