Giải thích các bước giải:
`4. a) 2/3 + 4/3 : (-8/9)`
`= 2/3 + (-3/2) = -5/6`
`b) 9/11 + (-2/5 + 1/6) : 11/30`
`= 9/11 + (-7/30) : 11/30`
`= 9/11 + (-7/11) = 2/11`
`c) (0,7 - 1/5)` : 5/2³
`= 1/2 : 5/8 = 4/5`
`d) -2/7 × 3/11 + (-2/7) × 8/11 + 4/7`
`= -2/7 × 3/11 + (-2/7) × 8/11 + (-2/7) × (-2/7)`
`= -2/7 × [3/11 + 8/11 + (-2/7)]`
`= -2/7 × 5/7 = -10/49`
`5. a) -3/4 × 7/6 + 5/6 × -3/4`
`= -3/4 × (7/6 + 5/6)`
`= -3/4 × 2 = -3/2`
`b) -17/25 × 20/33 + (-17/25) × 13/33 + (-3/25)`
`= -17/25 × (20/33 + 13/33) + (-3/25)`
`= -17/25 × 1 + (-3/25)`
`= -17/25 + (-3/25) = -4/5`