Đáp án+Giải thích các bước giải:
`a) 3/7 xx 5/6 + 5/6 xx 4/7`
`= 5/6 xx (3/7+4/7)`
`= 5/6 xx 7/7`
`= 5/6 xx 1`
`= 5/6`
`b) 4/9 xx 5/6 - 1/3 xx 4/9`
`= 4/9 xx ( 5/6 - 1/3)`
`= 4/9 xx ( 5/6 - 2/6)`
`= 4/9 xx 3/6`
`= 4/9 xx 1/2`
`= 2/9`
`c) 1/6 : 4/5 + 1/8 : 4/5 `
`= ( 1/6 + 1/8) : 4/5`
`= ( 4/24 + 3/24) : 4/5`
`= 7/24 : 4/5`
`= 7/24 xx 5/4`
`= 35/96`
`d) 1/6 : 4/5 - 1/8 : 4/5`
`= (1/6-1/8) : 4/5`
`= (4/24-3/24) : 4/5`
`= 1/24 : 4/5`
`= 1/24 xx 5/4`
`= 5/96`