Đáp án:
$\\$
`a,`
`3 1/9 × 7/6 + 7/6 ÷ (-3)^2 -1 1/2`
`= 28/9 × 7/6 + 7/6 ÷ 9 - 3/2`
`= 28/9 × 7/6 - 7/6×1/9 - 3/2`
`= 7/6 × (28/9 - 1/9)/ - 3/2`
`= 7/6 × 3 - 3/2`
`= 7/2 - 3/2`
`= 2`
$\\$
`b,`
`3/2021 × 1/7 + 3/7 ÷ 2021/2020 - (-4)/7`
`= 1/2021 × 3/7 + 3/7 × 2020/2021 + 4/7`
`= 3/7 × (1/2021 + 2020/2021) + 4/7`
`= 3/7 × 1 + 4/7`
`= 3/7 + 4/7`
`= 1`
$\\$
`c,`
`(-5)^2 × 47 + 25 × (-31) + 60 × (-5)`
`= 25 × 47 + 25 × (-31) + 60 × (-5)`
`= 25 × [47 + (-31)] + 60×(-5)`
`= 25 ×16 - 60 × 5`
`= 5 × 5 × 16 - 60 × 5`
`= 5 × 80 - 60×5`
`= 5 × (80-60)`
`= 5×20`
`= 100`
