Đáp án:
`A=7/19 . 8/11 + 7/19 . 3/11 + 12/19`
`A=7/19 (8/11 + 3/11) + 12/19`
`A=7/19 . 11/11 + 12/19`
`A=1`
`B=5/9 . 7/13 + 5/9 . 9/13 - 5/9 . 3/13`
`B=5/9 (7/13 + 3/13 - 3/13)`
`B=5/9 . 1`
`B=5/9`
`C=(67/111 + 2/33 - 15/117) . (1/3 - 1/4 - 1/12)`
`C=(67/111 + 2/33 - 15/117) .0`
`C=67/111 + 2/33 - 15/117) . 0`
`C=0`