`(27,54 × 1,1 - 279,24 × 0,1) : 0,3`
`= (30,294 - 27,924) : 0,3`
`= 2,37 : 0,3`
`= 7,9`
_____
$\dfrac{\dfrac{36}{41} : \dfrac{9}{41}}{\dfrac{14}{21} : \dfrac{7}{21}}$ `× 2/5`
$= \dfrac{\dfrac{36}{41} × \dfrac{41}{9}}{\dfrac{14}{21} × \dfrac{21}{7}}$ `× 2/5`
$= \dfrac{\dfrac{36}{9}}{\dfrac{14}{7}}$ `× 2/5`
`= 4/2 × 2/5`
`= 2 × 2/5`
`= 4/5`