`(3/5 - 2/3 - 4/(-15)) . 5/6+1/6`
`= (9/15 - 10/15 + 4/15) . 5/6+1/6`
`= ((-1)/15 + 4/15) . 5/6+1/6`
`= 1/5 . 5/6+1/6`
`=1/6 + 1/6`
`= 1/3`
`(-8)/27 . 11/15 + 2019 . 8/27 + 4/15 . (-8/27)`
`= 8/27 . (-11)/15 + 2019 . 8/27 + (-4)/15 . 8/27`
`= 8/27 . ((-11)/15 + (-4)/15 + 2019)`
`= 8/27 . (-1 + 2019)`
`= 8/27 . 2018`
`= 16144/27`
(Chúc bạn học tốt)