Đáp án:
`a,`
`3/5 + 13/25 - 5/9 - 6/14`
`= (3/5 + 13/25 - 5/9)- 6/14`
`= (28/25 - 5/9) - 6/14`
`= 127/225 - 6/14`
`= 214/1575`
`b,`
`[(1/9 ÷ 8/27) ÷ (-1)/3] ÷ 81/128`
`= [(1/9 × 27/8) × (-3)] × 128/81`
`= [3/8 × (-3)] × 128/81`
`= (-9)/8 × 128/81`
`= (-16)/9`
`c,`
`(-7/15) × 5/8 × 15/(-7) × (-32)`
`= (-7/15 × 15/(-7)) × (-32 × 5/8)`
`= 1 × (-20)`
`= -20`