Bài 1 :
a, `8/9` - `1/3` : `1/2` + `1/3`
= `8/9` - `1/3` x 2 + `1/3`
= `16/18` - `12/18` + `6/18`
= `10/18`
= `5/9`
b, `3/10` + `1/2` x `1/3` - `1/3`
= `9/30` + `5/30` - `10/30`
= `4/30`
= `2/15`
c, `2/5` : `7/10` + `2/7` x `1/2`
= `20/35` + `2/14`
= `4/7` + `1/7`
= `5/7`