Giải thích các bước giải:
a) `2/3` - `4/7` + `1/3`
= (`2/3` + `1/3` ) - `4/7`
= 1 - `4/7`
=`3/7`
b) `2/3` - `5/7` . `14/15`
= `2/3` - `( 5 .14 )/(7 . 15)`
= `2/3` - `( 1 . 2 )/( 1 . 3)`
= `2/3` - `2/3`
= 0
c) `7/19` . `8/11` + `7/19` . `3/11` + `12/19`
= `7/19` . ( `8/11` + `3/11`) + `12/19`
= `7/19` . 1 + `12/19`
= `7/19` + `12/19`
= 1