`a, A = -6 . {-2}/3 . 0,25`
`A = 3 . 0,25`
`A = 0,75`
$\text{Vậy}$ `A = 0,75`
____________________
`b, B = {-15}/4 . {-7}/15 . (-2 2/5)`
`B = 7/4 . (-12/5)`
`B = {-21}/5`
$\text{Vậy}$ `B = {-21}/5`
____________________
`c, C = {-5}/11 . 7/15 . 11/{-5} . (-30)`
`C = {-7}/33 . 11/{-5} . (-30)`
`C = 7/15 . (-30)`
`C = -14`
$\text{Vậy}$ `C = -14`
______________________
`d, D = {-5}/9 . 3/11 + {-13}/18 . 3/11`
`D = 3/11 . ({-5}/9 + {-13}/18)`
`D = 3/11 . {-23}/18`
`D = -23/66`
$\text{Vậy}$ `D = -23/66`