@ Đạt em
Đáp án + Cách làm :
a) `-8/15` + `7/9` - `11/12`
= ( `-8/15` + `7/9` ) - `11/12`
= `11/45` - `11/12`
= `-121/180`
b) `-1/2` × `4/9` + `3/7` × `15/14`
= ( `-1/2` × `4/9` ) + ( `3/7` × `15/14` )
= `-2/9` + `45/98`
= `209/882`
c) 8 `2/7` -( 2 `4/9` + 4 `2/7` )
= 8 `2/7` - 2 `4/9` - 4 `2/7`
= (8 `2/7` - 4 `2/7` ) - 2 `4/9`
= ( `58/7` - `30/7` ) - `22/9`
= `28/7` - `22/9`
= 4 - `22/9`
= `36/9` - `22/9`
= `14/9`